diff --git a/benchmark/binary_trees.wren b/benchmark/binary_trees.wren
index d880850b..0100e522 100644
--- a/benchmark/binary_trees.wren
+++ b/benchmark/binary_trees.wren
@@ -24,7 +24,7 @@ var minDepth = 4
 var maxDepth = 12
 var stretchDepth = maxDepth + 1
 
-var start = OS.clock
+var start = IO.clock
 
 IO.print("stretch tree of depth " + stretchDepth.toString + " check: " +
     new Tree(0, stretchDepth).check.toString)
@@ -53,4 +53,4 @@ while (depth < stretchDepth) {
 IO.print("long lived tree of depth " + maxDepth.toString + " check: " +
     longLivedTree.check.toString)
 
-IO.print("elapsed: " + (OS.clock - start).toString)
+IO.print("elapsed: " + (IO.clock - start).toString)
diff --git a/benchmark/fib.wren b/benchmark/fib.wren
index 637dfe99..3df1eea2 100644
--- a/benchmark/fib.wren
+++ b/benchmark/fib.wren
@@ -3,8 +3,8 @@ var fib = fn(n) {
   return fib.call(n - 1) + fib.call(n - 2)
 }
 
-var start = OS.clock
+var start = IO.clock
 for (i in 1..5) {
   IO.print(fib.call(28))
 }
-IO.print("elapsed: " + (OS.clock - start).toString)
+IO.print("elapsed: " + (IO.clock - start).toString)
diff --git a/benchmark/for.wren b/benchmark/for.wren
index 0195e347..c5c59a47 100644
--- a/benchmark/for.wren
+++ b/benchmark/for.wren
@@ -1,10 +1,10 @@
 var list = []
 
-var start = OS.clock
+var start = IO.clock
 for (i in 0...1000000) list.add(i)
 
 var sum = 0
 for (i in list) sum = sum + i
 
 IO.print(sum)
-IO.print("elapsed: " + (OS.clock - start).toString)
+IO.print("elapsed: " + (IO.clock - start).toString)
diff --git a/benchmark/method_call.wren b/benchmark/method_call.wren
index b686ba2a..8f377e04 100644
--- a/benchmark/method_call.wren
+++ b/benchmark/method_call.wren
@@ -28,7 +28,7 @@ class NthToggle is Toggle {
   }
 }
 
-var start = OS.clock
+var start = IO.clock
 var n = 100000
 var val = true
 var toggle = new Toggle(val)
@@ -66,4 +66,4 @@ for (i in 0...n) {
 
 IO.print(ntoggle.value)
 
-IO.print("elapsed: " + (OS.clock - start).toString)
+IO.print("elapsed: " + (IO.clock - start).toString)
diff --git a/src/wren_core.c b/src/wren_core.c
index 4afaa867..1ff439ef 100644
--- a/src/wren_core.c
+++ b/src/wren_core.c
@@ -2,7 +2,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
 
 #include "wren_core.h"
 #include "wren_value.h"
@@ -731,12 +730,6 @@ DEF_NATIVE(string_subscript)
   RETURN_VAL(value);
 }
 
-DEF_NATIVE(os_clock)
-{
-  double time = (double)clock() / CLOCKS_PER_SEC;
-  RETURN_NUM(time);
-}
-
 static ObjClass* defineSingleClass(WrenVM* vm, const char* name)
 {
   size_t length = strlen(name);
@@ -899,9 +892,6 @@ void wrenInitializeCore(WrenVM* vm)
   NATIVE(vm->stringClass, "!= ", string_bangeq);
   NATIVE(vm->stringClass, "[ ]", string_subscript);
 
-  ObjClass* osClass = defineClass(vm, "OS");
-  NATIVE(osClass->metaclass, "clock", os_clock);
-
   wrenInterpret(vm, "Wren core library", libSource);
 
   vm->listClass = AS_CLASS(findGlobal(vm, "List"));
diff --git a/src/wren_io.c b/src/wren_io.c
index e570d0e8..b57292d8 100644
--- a/src/wren_io.c
+++ b/src/wren_io.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <time.h>
 
 #include "wren_io.h"
 
@@ -17,15 +18,21 @@ static const char* libSource =
 "  }\n"
 "}\n";
 
-static void writeString(WrenVM* vm)
+static void ioWriteString(WrenVM* vm)
 {
   const char* s = wrenGetArgumentString(vm, 1);
   // TODO: Check for null.
   printf("%s", s);
 }
 
+static void ioClock(WrenVM* vm)
+{
+  wrenReturnDouble(vm, (double)clock() / CLOCKS_PER_SEC);
+}
+
 void wrenLoadIOLibrary(WrenVM* vm)
 {
   wrenInterpret(vm, "Wren IO library", libSource);
-  wrenDefineStaticMethod(vm, "IO", "writeString_", 1, writeString);
+  wrenDefineStaticMethod(vm, "IO", "writeString_", 1, ioWriteString);
+  wrenDefineStaticMethod(vm, "IO", "clock", 0, ioClock);
 }