diff --git a/AK/StdLibExtras.cpp b/AK/StdLibExtras.cpp
index e0caab308d3..4ce0c64dd5e 100644
--- a/AK/StdLibExtras.cpp
+++ b/AK/StdLibExtras.cpp
@@ -5,6 +5,7 @@
 
 extern "C" {
 
+#if ARCH(I386)
 #ifndef KERNEL
 void* mmx_memcpy(void* dest, const void* src, size_t len)
 {
@@ -54,6 +55,7 @@ void* mmx_memcpy(void* dest, const void* src, size_t len)
     return dest;
 }
 #endif
+#endif
 
 #ifdef KERNEL