diff --git a/src/arch/x86/lib/memcpy.c b/src/arch/x86/lib/memcpy.c
index 7f079ce9d6..4915a9eb51 100644
--- a/src/arch/x86/lib/memcpy.c
+++ b/src/arch/x86/lib/memcpy.c
@@ -5,8 +5,13 @@ void *memcpy(void *dest, const void *src, size_t n)
 	unsigned long d0, d1, d2;
 
 	asm volatile(
+#ifdef __x86_64__
+		"rep ; movsd\n\t"
+		"mov %4,%%rcx\n\t"
+#else
 		"rep ; movsl\n\t"
 		"movl %4,%%ecx\n\t"
+#endif
 		"rep ; movsb\n\t"
 		: "=&c" (d0), "=&D" (d1), "=&S" (d2)
 		: "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)