diff --git a/src/core/io.zig b/src/core/io.zig
index 495fd7d..ad814dc 100644
--- a/src/core/io.zig
+++ b/src/core/io.zig
@@ -63,10 +63,12 @@ pub fn Spliterator(comptime Element: type) type {
                 fn testEquality(this: Element, that: Element) bool {
                     return this == that;
                 }
-            }.testEquality)) |index| {
-                defer self.source = self.source[(index + self.delimiter.len) .. self.source.len];
+            }.testEquality)) |head| {
+                const tail = (head + self.delimiter.len);
 
-                return self.source[0 .. index];
+                defer self.source = self.source[tail .. self.source.len];
+
+                return self.source[0 .. (tail - 1)];
             }
 
             defer self.source = self.source[self.source.len .. self.source.len];
@@ -254,17 +256,15 @@ test "Find first of element" {
 pub fn findFirstOf(comptime Element: type, haystack: []const Element,
     needle: []const Element, comptime testEquality: fn (Element, Element) bool) ?usize {
 
-    var cursor: usize = 0;
-    const end = (haystack.len - needle.len);
+    var head: usize = 0;
+    const tail = (haystack.len - needle.len);
 
-    walk_haystack: while (cursor <= end) : (cursor += 1) {
-        const range = (cursor + needle.len);
-        var index = cursor;
+    walk_haystack: while (head <= tail) : (head += 1) {
+        for (needle) |element, index| {
+            if (!testEquality(haystack[head + index], element)) continue: walk_haystack;
+        }
 
-        while (index < range) : (index += 1)
-            if (testEquality(haystack[index], needle[index])) continue: walk_haystack;
-
-        return cursor;
+        return head;
     }
 
     return null;