diff --git a/builtins.cpp b/builtins.cpp
index 93d5c20c..2608e031 100644
--- a/builtins.cpp
+++ b/builtins.cpp
@@ -386,6 +386,7 @@ lSetInternalFunctions(llvm::Module *module) {
         "__ceil_uniform_float",
         "__ceil_varying_double",
         "__ceil_varying_float",
+        "__clock",
         "__count_trailing_zeros_i32",
         "__count_trailing_zeros_i64",
         "__count_leading_zeros_i32",