diff --git a/debug/app.ona b/debug/app.ona
index f05118d..9407ffe 100644
--- a/debug/app.ona
+++ b/debug/app.ona
@@ -1,12 +1,14 @@
 
-let printer = lambda ():
+let printer = lambda (pfx):
+	let prefix = pfx
+
 	return lambda (msg):
-		@print("This is a func call")
+		@print(prefix)
 		@print(msg)
 	end
 end
 
-let pr = printer()
+let pr = printer("This is a func call")
 var i = 0
 
 pr("test")
@@ -25,6 +27,10 @@ else:
 	pr("i'unno")
 end
 
+let pr2 = printer("this is a final closure")
+
+pr2("goodbye")
+
 return {
 	.title = "Game",
 	.width = 1280,
diff --git a/source/ona/file.zig b/source/ona/file.zig
index b05ae92..73a5b98 100644
--- a/source/ona/file.zig
+++ b/source/ona/file.zig
@@ -11,9 +11,9 @@ pub const Access = union (enum) {
 			.null => return null,
 
 			.sandboxed_path => |sandboxed_path| {
-				const readable_path_string = sandboxed_path.joined(readable_path).to_string() orelse return null;
+				const path_string = sandboxed_path.joined(readable_path).get_string();
 
-				return @ptrCast(ext.SDL_RWFromFile(readable_path_string.ptr, "rb"));
+				return @ptrCast(ext.SDL_RWFromFile(path_string.ptr, "rb"));
 			},
 		}
 	}
@@ -23,7 +23,7 @@ pub const Access = union (enum) {
 			.null => return null,
 
 			.sandboxed_path => |sandboxed_path| {
-				const path_string = sandboxed_path.joined(path).to_string() orelse return null;
+				const path_string = sandboxed_path.joined(path).get_string();
 				const rw_ops = ext.SDL_RWFromFile(path_string, "rb") orelse return null;
 				const file_size = ext.SDL_RWseek(rw_ops, 0, ext.RW_SEEK_END);
 
@@ -96,12 +96,8 @@ pub const Path = extern struct {
 		return path;
 	}
 
-	pub fn to_string(self: Path) ?[:0]const coral.io.Byte {
-		const last_index = self.data.len - 1;
-
-		if (self.data[last_index] != 0) {
-			return null;
-		}
+	pub fn get_string(self: Path) [:0]const coral.io.Byte {
+		coral.debug.assert(self.data[self.data.len - 1] == 0);
 
 		return coral.io.slice_sentineled(@as(coral.io.Byte, 0), @as([*:0]const coral.io.Byte, @ptrCast(&self.data)));
 	}
diff --git a/source/ona/kym.zig b/source/ona/kym.zig
index d56c80f..12fbf32 100644
--- a/source/ona/kym.zig
+++ b/source/ona/kym.zig
@@ -2,10 +2,6 @@ const Chunk = @import("./kym/Chunk.zig");
 
 const Table = @import("./kym/Table.zig");
 
-const app = @import("./app.zig");
-
-const builtin = @import("builtin");
-
 const coral = @import("coral");
 
 const file = @import("./file.zig");
@@ -15,7 +11,7 @@ const tokens = @import("./kym/tokens.zig");
 const tree = @import("./kym/tree.zig");
 
 pub const Frame = struct {
-	name: []const coral.io.Byte = "",
+	name_stringable: *RuntimeRef,
 	arg_count: u8,
 	locals_top: usize,
 
@@ -88,11 +84,11 @@ pub const RuntimeEnv = struct {
 			try self.locals.push_one(try self.acquire(arg));
 		}
 
-		const frame = try self.push_frame(args.len);
+		const frame = try self.push_frame(callable, args.len);
 
 		defer self.pop_frame();
 
-		return self.call_frame(callable, frame);
+		return self.call_frame(frame);
 	}
 
 	pub fn call_frame(self: *RuntimeEnv, callable: *const RuntimeRef, frame: Frame) RuntimeError!?*RuntimeRef {
@@ -132,6 +128,12 @@ pub const RuntimeEnv = struct {
 			switch (object.payload) {
 				.false, .true, .float, .fixed, .symbol, .vector2, .vector3, .syscall => {},
 
+				.boxed => |*boxed| {
+					if (boxed.*) |boxed_value| {
+						self.discard(boxed_value);
+					}
+				},
+
 				.string => |string| {
 					coral.debug.assert(string.len >= 0);
 					self.allocator.deallocate(string.ptr[0 .. @intCast(string.len)]);
@@ -201,6 +203,7 @@ pub const RuntimeEnv = struct {
 			.string => self.raise(error.TypeMismatch, "string is not get-indexable"),
 			.symbol => self.raise(error.TypeMismatch, "symbol is not get-indexable"),
 			.syscall => self.raise(error.TypeMismatch, "syscall is not get-indexable"),
+			.boxed => self.raise(error.TypeMismatch, "boxed is not get-indexable"),
 
 			.vector2 => |vector2| swizzle: {
 				const swizzle_symbol = try self.unbox_symbol(index);
@@ -258,6 +261,8 @@ pub const RuntimeEnv = struct {
 	}
 
 	pub fn import(self: *RuntimeEnv, file_path: file.Path) RuntimeError!?*RuntimeRef {
+		const file_name = file_path.get_string();
+
 		var chunk = make_chunk: {
 			const file_data =
 				(try file.allocate_and_load(self.allocator, self.options.import_access, file_path)) orelse {
@@ -282,24 +287,17 @@ pub const RuntimeEnv = struct {
 				};
 			}
 
-			break: make_chunk try Chunk.make(self, file_path.to_string() orelse "<script>", &root.environment);
+			break: make_chunk try Chunk.make(self, file_name, &root.environment);
 		};
 
-		if (builtin.mode == .Debug) {
-			const string_ref = try chunk.dump(self);
-
-			defer self.discard(string_ref);
-
-			const string = string_ref.as_string();
-
-			coral.debug.assert(string != null);
-			app.log_info(string.?);
-		}
-
 		defer chunk.free(self);
 
 		return execute_chunk: {
-			const frame = try self.push_frame(0);
+			const name = try self.new_string(file_name);
+
+			defer self.discard(name);
+
+			const frame = try self.push_frame(name, 0);
 
 			defer self.pop_frame();
 
@@ -357,11 +355,20 @@ pub const RuntimeEnv = struct {
 		});
 	}
 
+	pub fn new_boxed(self: *RuntimeEnv, value: ?*const RuntimeRef) RuntimeError!*RuntimeRef {
+		return RuntimeRef.allocate(self.allocator, .{
+			.ref_count = 1,
+			.payload = .{.boxed = if (value) |ref| ref.acquire() else null},
+		});
+	}
+
 	pub fn new_dynamic(
 		self: *RuntimeEnv,
-		userdata: [*]const coral.io.Byte,
+		userdata: []const coral.io.Byte,
 		typeinfo: *const Typeinfo,
 	) RuntimeError!*RuntimeRef {
+		coral.debug.assert(userdata.len == typeinfo.size);
+
 		const dynamic = try self.allocator.reallocate(null, @sizeOf(usize) + typeinfo.size);
 
 		errdefer self.allocator.deallocate(dynamic);
@@ -440,7 +447,7 @@ pub const RuntimeEnv = struct {
 
 		errdefer table.free(self);
 
-		return try self.new_dynamic(coral.io.bytes_of(&table).ptr, Table.typeinfo);
+		return try self.new_dynamic(coral.io.bytes_of(&table), Table.typeinfo);
 	}
 
 	pub fn new_vector2(self: *RuntimeEnv, x: f32, y: f32) RuntimeError!*RuntimeRef {
@@ -470,14 +477,23 @@ pub const RuntimeEnv = struct {
 	}
 
 	pub fn pop_frame(self: *RuntimeEnv) void {
-		var to_pop = self.locals.values.len - (self.frames.pop() orelse unreachable).locals_top;
+		const popped_frame = self.frames.pop();
 
-		while (to_pop != 0) {
-			if (self.locals.pop() orelse unreachable) |local| {
+		coral.debug.assert(popped_frame != null);
+		self.discard(popped_frame.?.name_stringable);
+
+		var locals_to_pop = self.locals.values.len - popped_frame.?.locals_top;
+
+		while (locals_to_pop != 0) {
+			const popped_local = self.locals.pop();
+
+			coral.debug.assert(popped_local != null);
+
+			if (popped_local.?) |local| {
 				self.discard(local);
 			}
 
-			to_pop -= 1;
+			locals_to_pop -= 1;
 		}
 	}
 
@@ -485,8 +501,9 @@ pub const RuntimeEnv = struct {
 		return self.locals.pop() orelse self.raise(error.IllegalState, "stack underflow");
 	}
 
-	pub fn push_frame(self: *RuntimeEnv, arg_count: u8) RuntimeError!Frame {
+	pub fn push_frame(self: *RuntimeEnv, name_stringable: *RuntimeRef, arg_count: u8) RuntimeError!Frame {
 		const frame = Frame{
+			.name_stringable = name_stringable.acquire(),
 			.arg_count = arg_count,
 			.locals_top = self.locals.values.len - arg_count,
 		};
@@ -507,7 +524,17 @@ pub const RuntimeEnv = struct {
 			while (remaining_frames != 0) {
 				remaining_frames -= 1;
 
-				self.print_error(self.frames.values[remaining_frames].name);
+				const callable_string = try self.to_string(self.frames.values[remaining_frames].name_stringable);
+
+				defer self.discard(callable_string);
+
+				self.print_error(get_name: {
+					const string = callable_string.as_string();
+
+					coral.debug.assert(string != null);
+
+					break: get_name string.?;
+				});
 			}
 		}
 
@@ -573,6 +600,7 @@ pub const RuntimeEnv = struct {
 				break: convert self.new_string(string[0 .. length.?]);
 			},
 
+			.boxed => unreachable,
 			.symbol => |symbol| self.new_string(coral.io.slice_sentineled(@as(coral.io.Byte, 0), symbol)),
 			.string => value.acquire(),
 
@@ -661,6 +689,7 @@ pub const RuntimeRef = opaque {
 			vector2: [2]f32,
 			vector3: [3]f32,
 			syscall: *const Syscall,
+			boxed: ?*RuntimeRef,
 
 			string: struct {
 				ptr: [*]coral.io.Byte,
@@ -712,9 +741,23 @@ pub const RuntimeRef = opaque {
 		return @ptrCast(try coral.io.allocate_one(allocator, data));
 	}
 
+	pub fn as_boxed(self: *const RuntimeRef) ?*?*RuntimeRef {
+		return switch (self.object().payload) {
+			.boxed => |*boxed| boxed,
+			else => null,
+		};
+	}
+
+	pub fn as_dynamic(self: *const RuntimeRef, typeinfo: *const Typeinfo) ?[]u8 {
+		return switch (self.object().payload) {
+			.dynamic => |dynamic| if (dynamic.typeinfo() == typeinfo) dynamic.userdata() else null,
+			else => null,
+		};
+	}
+
 	pub fn as_fixed(self: *const RuntimeRef) ?Fixed {
 		return switch (self.object().payload) {
-			.fixed => |fixed| @intCast(@as(u32, @bitCast(fixed))),
+			.fixed => |fixed| fixed,
 			else => null,
 		};
 	}
@@ -727,6 +770,7 @@ pub const RuntimeRef = opaque {
 				break: get string.ptr[0 .. @intCast(string.len)];
 			},
 
+			.symbol => |symbol| coral.io.slice_sentineled(@as(u8, 0), symbol),
 			else => null,
 		};
 	}
@@ -757,6 +801,8 @@ pub const RuntimeRef = opaque {
 				else => false,
 			},
 
+			.boxed => unreachable,
+
 			.vector2 => |self_vector| switch (other.object().payload) {
 				.vector2 => |other_vector| coral.io.are_equal(coral.io.bytes_of(&self_vector), coral.io.bytes_of(&other_vector)),
 				else => false,
@@ -797,6 +843,7 @@ pub const RuntimeRef = opaque {
 			.vector2 => |vector| @bitCast(vector),
 			.vector3 => |vector| coral.io.jenkins_hash(@typeInfo(usize).Int, coral.io.bytes_of(&vector)),
 			.syscall => |syscall| @intFromPtr(syscall),
+			.boxed => |boxed| @intFromPtr(boxed),
 			.string => |string| coral.io.djb2_hash(@typeInfo(usize).Int, string.unpack()),
 			.dynamic => |dynamic| @intFromPtr(dynamic.typeinfo()) ^ @intFromPtr(dynamic.userdata().ptr),
 		};
@@ -812,6 +859,7 @@ pub const RuntimeRef = opaque {
 			.vector2 => |vector| coral.io.all_equals(coral.io.bytes_of(&vector), 0),
 			.vector3 => |vector| coral.io.all_equals(coral.io.bytes_of(&vector), 0),
 			.syscall => true,
+			.boxed => |boxed| boxed != null,
 			.string => |string| string.len != 0,
 			.dynamic => true,
 		};
diff --git a/source/ona/kym/Chunk.zig b/source/ona/kym/Chunk.zig
index 2fd7328..758fb9e 100644
--- a/source/ona/kym/Chunk.zig
+++ b/source/ona/kym/Chunk.zig
@@ -1,5 +1,9 @@
+const app = @import("../app.zig");
+
 const Compiler = @import("./Compiler.zig");
 
+const builtin = @import("builtin");
+
 const coral = @import("coral");
 
 const file = @import("../file.zig");
@@ -12,6 +16,11 @@ name: *kym.RuntimeRef,
 arity: u8,
 opcodes: OpcodeList,
 constants: ConstList,
+bindings: []?*kym.RuntimeRef,
+
+const Box = struct {
+
+};
 
 const Builtin = enum {
 	import,
@@ -32,13 +41,15 @@ const OpcodeList = coral.list.Stack(union (enum) {
 	push_top,
 	push_table: u32,
 	push_builtin: Builtin,
-	push_closure: u8,
-	push_self,
+	push_binding: u8,
 	push_boxed,
 	set_local: u8,
 	get_dynamic,
 	set_dynamic,
+	get_box,
+	set_box,
 	call: u8,
+	bind: u8,
 
 	not,
 	neg,
@@ -67,6 +78,7 @@ pub fn dump(chunk: Self, env: *kym.RuntimeEnv) kym.RuntimeError!*kym.RuntimeRef
 	defer buffer.free();
 
 	const writer = coral.list.stack_as_writer(&buffer);
+
 	_ = coral.utf8.print_string(writer, coral.io.slice_sentineled(@as(coral.io.Byte, 0), try env.unbox_symbol(chunk.name)));
 
 	_ = coral.utf8.print_string(writer, ":\n");
@@ -107,10 +119,9 @@ pub fn dump(chunk: Self, env: *kym.RuntimeEnv) kym.RuntimeError!*kym.RuntimeRef
 			}),
 
 			.push_boxed => coral.utf8.print_string(writer, "push boxed\n"),
-			.push_self => coral.utf8.print_string(writer, "push self\n"),
 
-			.push_closure => |push_closure| coral.utf8.print_formatted(writer, "push closure <{count}>\n", .{
-				.count = push_closure,
+			.push_binding => |push_binding| coral.utf8.print_formatted(writer, "push binding <{binding}>\n", .{
+				.binding = push_binding,
 			}),
 
 			.push_builtin => |push_builtin| coral.utf8.print_formatted(writer, "push builtin <{builtin}>\n", .{
@@ -122,7 +133,16 @@ pub fn dump(chunk: Self, env: *kym.RuntimeEnv) kym.RuntimeError!*kym.RuntimeRef
 				},
 			}),
 
-			.set_local => |local_set| coral.utf8.print_formatted(writer, "set local <{local}>\n", .{.local = local_set}),
+			.bind => |bind| coral.utf8.print_formatted(writer, "bind <{count}>\n", .{
+				.count = bind,
+			}),
+
+			.set_local => |local_set| coral.utf8.print_formatted(writer, "set local <{local}>\n", .{
+				.local = local_set,
+			}),
+
+			.get_box => coral.utf8.print_string(writer, "get box\n"),
+			.set_box => coral.utf8.print_string(writer, "set box\n"),
 			.get_dynamic => coral.utf8.print_string(writer, "get dynamic\n"),
 			.set_dynamic => coral.utf8.print_string(writer, "set dynamic\n"),
 			.call => |call| coral.utf8.print_formatted(writer, "call <{count}>\n", .{.count = call}),
@@ -145,11 +165,11 @@ pub fn dump(chunk: Self, env: *kym.RuntimeEnv) kym.RuntimeError!*kym.RuntimeRef
 	return env.new_string(buffer.values);
 }
 
-pub fn execute(chunk: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeError!?*kym.RuntimeRef {
+pub fn execute(self: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeError!?*kym.RuntimeRef {
 	var opcode_cursor = @as(u32, 0);
 
-	while (opcode_cursor < chunk.opcodes.values.len) : (opcode_cursor += 1) {
-		switch (chunk.opcodes.values[opcode_cursor]) {
+	while (opcode_cursor < self.opcodes.values.len) : (opcode_cursor += 1) {
+		switch (self.opcodes.values[opcode_cursor]) {
 			.pop => {
 				if (try env.pop_local()) |ref| {
 					env.discard(ref);
@@ -161,11 +181,11 @@ pub fn execute(chunk: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeE
 			.push_false => try env.locals.push_one(try env.new_boolean(false)),
 
 			.push_const => |push_const| {
-				if (push_const >= chunk.constants.values.len) {
+				if (push_const >= self.constants.values.len) {
 					return env.raise(error.IllegalState, "invalid constant");
 				}
 
-				try env.locals.push_one(chunk.constants.values[push_const].acquire());
+				try env.locals.push_one(self.constants.values[push_const].acquire());
 			},
 
 			.push_local => |push_local| {
@@ -219,19 +239,59 @@ pub fn execute(chunk: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeE
 			},
 
 			.push_boxed => {
-				// TODO: Implement.
-				unreachable;
+				const value = try env.pop_local();
+
+				defer {
+					if (value) |ref| {
+						env.discard(ref);
+					}
+				}
+
+				const boxable = try env.new_boxed(value);
+
+				errdefer env.discard(boxable);
+
+				try env.locals.push_one(boxable);
 			},
 
-			.push_self => {
-				// TODO: Implement.
-				unreachable;
+			.push_binding => |push_binding| {
+				if (push_binding > self.bindings.len) {
+					return env.raise(error.IllegalState, "binding out of range");
+				}
+
+				try env.locals.push_one(if (self.bindings[push_binding]) |value| value.acquire() else null);
 			},
 
-			.push_closure => |push_closure| {
-				// TODO: Implement.
-				_ = push_closure;
-				unreachable;
+			.bind => |bind| {
+				const lambda = try env.expect(try env.pop_local());
+
+				errdefer env.discard(lambda);
+
+				const chunk = @as(*Self, @ptrCast(@alignCast(lambda.as_dynamic(typeinfo) orelse {
+					return env.raise(error.IllegalState, "cannot bind to non-chunk");
+				})));
+
+				chunk.bindings = try coral.io.allocate_many(env.allocator, bind, @as(?*kym.RuntimeRef, null));
+
+				for (0 .. bind) |index| {
+					const value = try env.pop_local();
+
+					errdefer {
+						if (value) |ref| {
+							env.discard(ref);
+						}
+					}
+
+					const binding = &chunk.bindings[index];
+
+					if (binding.*) |*existing_binding| {
+						env.discard(existing_binding.*);
+					}
+
+					binding.* = value;
+				}
+
+				try env.locals.push_one(lambda);
 			},
 
 			.push_builtin => |push_builtin| {
@@ -257,6 +317,34 @@ pub fn execute(chunk: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeE
 				local.* = try env.pop_local();
 			},
 
+			.get_box => {
+				const box = try env.expect(try env.pop_local());
+
+				defer env.discard(box);
+
+				const boxed = box.as_boxed() orelse {
+					return env.raise(error.TypeMismatch, "type is not unboxable");
+				};
+
+				try env.locals.push_one(if (boxed.*) |value| value.acquire() else null);
+			},
+
+			.set_box => {
+				const box = try env.expect(try env.pop_local());
+
+				errdefer env.discard(box);
+
+				const boxed = box.as_boxed() orelse {
+					return env.raise(error.TypeMismatch, "type is not unboxable");
+				};
+
+				if (boxed.*) |value| {
+					env.discard(value);
+				}
+
+				boxed.* = box;
+			},
+
 			.get_dynamic => {
 				const index = try env.expect(try env.pop_local());
 
@@ -307,7 +395,7 @@ pub fn execute(chunk: Self, env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeE
 
 					defer env.discard(callable);
 
-					const call_frame = try env.push_frame(call);
+					const call_frame = try env.push_frame(callable, call);
 
 					defer env.pop_frame();
 
@@ -494,6 +582,18 @@ pub fn free(self: *Self, env: *kym.RuntimeEnv) void {
 	self.constants.free();
 	self.opcodes.free();
 	env.discard(self.name);
+
+	if (self.bindings.len != 0) {
+		for (self.bindings) |binding| {
+			if (binding) |value| {
+				env.discard(value);
+			}
+		}
+
+		env.allocator.deallocate(self.bindings);
+	}
+
+	self.bindings = &.{};
 }
 
 pub fn make(env: *kym.RuntimeEnv, name: []const coral.io.Byte, environment: *const tree.Environment) kym.RuntimeError!Self {
@@ -501,6 +601,7 @@ pub fn make(env: *kym.RuntimeEnv, name: []const coral.io.Byte, environment: *con
 		.name = try env.new_symbol(name),
 		.opcodes = OpcodeList.make(env.allocator),
 		.constants = ConstList.make(env.allocator),
+		.bindings = &.{},
 		.arity = 0,
 	};
 
@@ -511,6 +612,17 @@ pub fn make(env: *kym.RuntimeEnv, name: []const coral.io.Byte, environment: *con
 
 	try compiler.compile_environment(environment);
 
+	if (builtin.mode == .Debug) {
+		const string_ref = try chunk.dump(env);
+
+		defer env.discard(string_ref);
+
+		const string = string_ref.as_string();
+
+		coral.debug.assert(string != null);
+		app.log_info(string.?);
+	}
+
 	return chunk;
 }
 
@@ -550,7 +662,7 @@ fn syscall_vec3(env: *kym.RuntimeEnv, frame: kym.Frame) kym.RuntimeError!?*kym.R
 
 pub const typeinfo = &kym.Typeinfo{
 	.size = @sizeOf(Self),
-	.name = "lambda",
+	.name = "func",
 	.destruct = typeinfo_destruct,
 	.call = typeinfo_call,
 };
diff --git a/source/ona/kym/Compiler.zig b/source/ona/kym/Compiler.zig
index 747639b..6fb8321 100644
--- a/source/ona/kym/Compiler.zig
+++ b/source/ona/kym/Compiler.zig
@@ -90,14 +90,18 @@ fn compile_expression(self: Self, environment: *const tree.Environment, expressi
 
 			errdefer chunk.free(self.env);
 
-			try self.chunk.opcodes.push_one(.{.push_const = try self.declare_chunk(chunk)});
-
-			if (lambda_construct.environment.capture_count != 0) {
-				for (lambda_construct.environment.captures[0 .. lambda_construct.environment.capture_count]) |capture| {
+			if (lambda_construct.environment.capture_count == 0 and environment.capture_count == 0) {
+				try self.chunk.opcodes.push_one(.{.push_const = try self.declare_chunk(chunk)});
+			} else {
+				for (environment.captures[0 .. environment.capture_count]) |capture| {
 					try self.chunk.opcodes.push_one(.{.push_local = environment.captures[capture]});
 				}
 
-				try self.chunk.opcodes.push_one(.{.push_closure = lambda_construct.environment.capture_count});
+				try self.chunk.opcodes.push_one(.{.push_const = try self.declare_chunk(chunk)});
+
+				try self.chunk.opcodes.push_one(.{
+					.bind = lambda_construct.environment.capture_count + environment.capture_count,
+				});
 			}
 		},
 
@@ -146,27 +150,34 @@ fn compile_expression(self: Self, environment: *const tree.Environment, expressi
 			}
 
 			if (get_capture_index(environment, declaration_get.declaration)) |index| {
-				try self.chunk.opcodes.push_one(.push_self);
-				try self.chunk.opcodes.push_one(.{.push_const = try self.declare_fixed(index)});
+				try self.chunk.opcodes.push_one(.{.push_binding = index});
 
-				return self.chunk.opcodes.push_one(.get_dynamic);
+				if (declaration_get.declaration.is.captured) {
+					try self.chunk.opcodes.push_one(.get_box);
+				}
+
+				return;
 			}
 
 			return self.env.raise(error.IllegalState, "local out of scope");
 		},
 
 		.declaration_set => |declaration_set| {
-			try self.compile_expression(environment, declaration_set.assign);
-
 			if (get_local_index(environment, declaration_set.declaration)) |index| {
+				try self.compile_expression(environment, declaration_set.assign);
+
 				return self.chunk.opcodes.push_one(.{.set_local = index});
 			}
 
 			if (get_capture_index(environment, declaration_set.declaration)) |index| {
-				try self.chunk.opcodes.push_one(.push_self);
-				try self.chunk.opcodes.push_one(.{.push_const = try self.declare_fixed(index)});
+				try self.chunk.opcodes.push_one(.{.push_binding = index});
+				try self.compile_expression(environment, declaration_set.assign);
 
-				return self.chunk.opcodes.push_one(.set_dynamic);
+				if (declaration_set.declaration.is.captured) {
+					try self.chunk.opcodes.push_one(.set_box);
+				}
+
+				return;
 			}
 
 			return self.env.raise(error.IllegalState, "local out of scope");
@@ -253,7 +264,7 @@ fn compile_statement(self: Self, environment: *const tree.Environment, initial_s
 			.declare => |declare| {
 				try self.compile_expression(environment, declare.initial_expression);
 
-				if (declare.declaration.is_captured and !declare.declaration.is_readonly) {
+				if (declare.declaration.is.captured and !declare.declaration.is.readonly) {
 					try self.chunk.opcodes.push_one(.push_boxed);
 				}
 			},
@@ -276,7 +287,7 @@ fn declare_chunk(self: Self, chunk: Chunk) kym.RuntimeError!u16 {
 		return self.env.raise(error.BadSyntax, "chunks cannot contain more than 65,535 constants");
 	}
 
-	const constant = try self.env.new_dynamic(coral.io.bytes_of(&chunk).ptr, Chunk.typeinfo);
+	const constant = try self.env.new_dynamic(coral.io.bytes_of(&chunk), Chunk.typeinfo);
 
 	errdefer self.env.discard(constant);
 
@@ -346,7 +357,11 @@ pub fn get_capture_index(self: *const tree.Environment, declaration: *const tree
 		var capture_index = @as(u8, 0);
 
 		while (capture_index < self.capture_count) : (capture_index += 1) {
-			if (&enclosing_environment.local_declarations[capture_index] == declaration) {
+			const captured_declaration_index = self.captures[capture_index];
+
+			coral.debug.assert(captured_declaration_index < enclosing_environment.local_declaration_count);
+
+			if (&enclosing_environment.local_declarations[captured_declaration_index] == declaration) {
 				return capture_index;
 			}
 		}
diff --git a/source/ona/kym/Expr.zig b/source/ona/kym/Expr.zig
index 4952fcb..799013a 100644
--- a/source/ona/kym/Expr.zig
+++ b/source/ona/kym/Expr.zig
@@ -174,11 +174,17 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 
 		return root.create_expr(.{
 			.kind = switch (expression.kind) {
-				.declaration_get => |declaration_get| .{
-					.declaration_set = .{
-						.assign = try parse(root, stream, environment),
-						.declaration = declaration_get.declaration,
-					},
+				.declaration_get => |declaration_get| convert: {
+					if (declaration_get.declaration.is.readonly) {
+						return root.report_error(stream, "readonly declarations cannot be re-assigned", .{});
+					}
+
+					break: convert .{
+						.declaration_set = .{
+							.assign = try parse(root, stream, environment),
+							.declaration = declaration_get.declaration,
+						},
+					};
 				},
 
 				.field_get => |field_get| .{
@@ -413,18 +419,19 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 		.identifier => |identifier| {
 			stream.skip_newlines();
 
+			const declaration = (try environment.resolve_declaration(identifier)) orelse {
+				return root.report_error(stream, "undefined identifier `{identifier}`", .{
+					.identifier = identifier,
+				});
+			};
+
+			if (declaration.is.argument and declaration.is.captured) {
+				return root.report_error(stream, "arguments cannot be directly captured, create a declaration", .{});
+			}
+
 			return root.create_expr(.{
 				.next = null,
-
-				.kind = .{
-					.declaration_get = .{
-						.declaration = (try environment.resolve_declaration(identifier)) orelse {
-							return root.report_error(stream, "undefined identifier `{identifier}`", .{
-								.identifier = identifier,
-							});
-						},
-					},
-				},
+				.kind = .{.declaration_get = .{.declaration = declaration}},
 			});
 		},
 
@@ -445,7 +452,10 @@ fn parse_operand(root: *tree.Root, stream: *tokens.Stream, environment: *tree.En
 					else => return root.report_error(stream, "expected identifier", .{}),
 				};
 
-				if (try lambda_environment.declare(identifier) == null) {
+				if (try lambda_environment.declare(.{
+					.identifier = identifier,
+					.is = .{.argument = true},
+				}) == null) {
 					return root.report_error(stream, "declaration `{identifier}` already exists", .{
 						.identifier = identifier,
 					});
diff --git a/source/ona/kym/Stmt.zig b/source/ona/kym/Stmt.zig
index 5f0dcc8..158d21e 100644
--- a/source/ona/kym/Stmt.zig
+++ b/source/ona/kym/Stmt.zig
@@ -122,7 +122,7 @@ pub fn parse(root: *tree.Root, stream: *tokens.Stream, environment: *tree.Enviro
 					.declare = .{
 						.initial_expression = try Expr.parse(root, stream, environment),
 
-						.declaration = (try root.environment.declare(identifier)) orelse {
+						.declaration = (try environment.declare(.{.identifier = identifier})) orelse {
 							return root.report_error(stream, "declaration `{identifier}` already exists", .{
 								.identifier = identifier,
 							});
diff --git a/source/ona/kym/tree.zig b/source/ona/kym/tree.zig
index 0438da0..9421e17 100644
--- a/source/ona/kym/tree.zig
+++ b/source/ona/kym/tree.zig
@@ -8,8 +8,12 @@ const tokens = @import("./tokens.zig");
 
 pub const Declaration = struct {
 	identifier: []const coral.io.Byte,
-	is_readonly: bool = false,
-	is_captured: bool = false,
+
+	is: packed struct {
+		readonly: bool = false,
+		captured: bool = false,
+		argument: bool = false,
+	} = .{},
 };
 
 pub const Environment = struct {
@@ -31,17 +35,17 @@ pub const Environment = struct {
 		});
 	}
 
-	pub fn declare(self: *Environment, identifier: []const coral.io.Byte) coral.io.AllocationError!?*const Declaration {
+	pub fn declare(self: *Environment, declaration: Declaration) coral.io.AllocationError!?*const Declaration {
 		if (self.local_declaration_count == self.local_declarations.len) {
 			return error.OutOfMemory;
 		}
 
-		const declaration = &self.local_declarations[self.local_declaration_count];
+		const declaration_slot = &self.local_declarations[self.local_declaration_count];
 
-		declaration.* = .{.identifier = identifier};
+		declaration_slot.* = declaration;
 		self.local_declaration_count += 1;
 
-		return declaration;
+		return declaration_slot;
 	}
 
 	pub fn resolve_declaration(self: *Environment, identifier: []const coral.io.Byte) coral.io.AllocationError!?*const Declaration {
@@ -49,20 +53,20 @@ pub const Environment = struct {
 		var ancestry = @as(usize, 0);
 
 		while (true) : (ancestry += 1) {
-			var remaining_count = self.local_declaration_count;
+			var remaining_count = environment.local_declaration_count;
 
 			while (remaining_count != 0) {
 				remaining_count -= 1;
 
-				const declaration = &self.local_declarations[remaining_count];
+				const declaration = &environment.local_declarations[remaining_count];
 
 				if (coral.io.are_equal(declaration.identifier, identifier)) {
 					if (ancestry != 0) {
-						declaration.is_captured = true;
+						declaration.is.captured = true;
 						environment = self;
 
 						while (ancestry != 0) : (ancestry -= 1) {
-							if (environment.capture_count == self.captures.len) {
+							if (environment.capture_count == environment.captures.len) {
 								return error.OutOfMemory;
 							}