diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 39e592d0e0b4..e478e40fbe5a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -30,12 +30,9 @@
 #define STATIC		static
 
 /*
- * Use normal definitions of mem*() from string.c. There are already
- * included header files which expect a definition of memset() and by
- * the time we define memset macro, it is too late.
+ * Provide definitions of memzero and memmove as some of the decompressors will
+ * try to define their own functions if these are not defined as macros.
  */
-#undef memcpy
-#undef memset
 #define memzero(s, n)	memset((s), 0, (n))
 #define memmove		memmove
 
diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
index 995f7b7ad512..a232da487cd2 100644
--- a/arch/x86/boot/string.h
+++ b/arch/x86/boot/string.h
@@ -11,10 +11,7 @@ void *memcpy(void *dst, const void *src, size_t len);
 void *memset(void *dst, int c, size_t len);
 int memcmp(const void *s1, const void *s2, size_t len);
 
-/*
- * Access builtin version by default. If one needs to use optimized version,
- * do "undef memcpy" in .c file and link against right string.c
- */
+/* Access builtin version by default. */
 #define memcpy(d,s,l) __builtin_memcpy(d,s,l)
 #define memset(d,c,l) __builtin_memset(d,c,l)
 #define memcmp	__builtin_memcmp