diff --git a/libc/src/string/memory_utils/op_x86.h b/libc/src/string/memory_utils/op_x86.h
--- a/libc/src/string/memory_utils/op_x86.h
+++ b/libc/src/string/memory_utils/op_x86.h
@@ -20,15 +20,21 @@
 #include "src/string/memory_utils/op_builtin.h"
 #include "src/string/memory_utils/op_generic.h"
 
-#ifdef __SSE2__
+#if defined(__AVX512F__) || defined(__SSE2__) || defined(__AVX2__)
 #include <immintrin.h>
-#else
+#endif
+
 // Define fake functions to prevent the compiler from failing on undefined
-// functions in case SSE2 is not present.
+// functions in case the builtin is not present.
+#ifndef __AVX512F__
 #define _mm512_cmpneq_epi8_mask(A, B) 0
+#endif //  __AVX512F__
+#ifndef __SSE2__
 #define _mm_movemask_epi8(A) 0
-#define _mm256_movemask_epi8(A) 0
 #endif //  __SSE2__
+#ifndef __AVX2__
+#define _mm256_movemask_epi8(A) 0
+#endif //  __AVX2__
 
 namespace __llvm_libc::x86 {