diff --git a/src/mem.h b/src/mem.h
index 1850839..fc01493 100644
--- a/src/mem.h
+++ b/src/mem.h
@@ -1,9 +1,15 @@
 #ifndef MEM_H
 #define MEM_H
 
-static inline void * memcpy(void * dest, const void * src, size_t n)
+static inline void memcpy(void * dest, const void * src, size_t n)
 {
-    return __builtin_memcpy(dest, src, n);
+    uint32_t r0, r1, r2;
+    __asm__ __volatile__ (
+            "cld\n\t"
+            "rep movsb"
+            : "=&c" (r0), "=&S" (r1), "=&D" (r2)
+            : "2" (dest), "1" (src), "0" (n)
+            : "memory");
 }
 
 static inline void * memmove(void * dest, const void * src, size_t count)