diff --git a/src/util/arch/x86/x86.h b/src/util/arch/x86/x86.h
index dae08149..3c909f89 100644
--- a/src/util/arch/x86/x86.h
+++ b/src/util/arch/x86/x86.h
@@ -58,15 +58,26 @@
 #define HAVE_SIMD_256_BITS
 #endif
 
-#if defined(__AVX512BW__)
+#if defined(__AVX512BW__) && defined(BUILD_AVX512)
 #define HAVE_AVX512
 #define HAVE_SIMD_512_BITS
 #endif
 
-#if defined(__AVX512VBMI__)
+#if defined(__AVX512VBMI__) && defined(BUILD_AVX512)
 #define HAVE_AVX512VBMI
 #endif
 
+#if defined(HAVE_SIMD_512_BITS)
+#define CHUNKSIZE 512
+#define VECTORSIZE 64
+#elif defined(HAVE_SIMD_256_BITS)
+#define CHUNKSIZE 256
+#define VECTORSIZE 32
+#elif defined(HAVE_SIMD_128_BITS)
+#define CHUNKSIZE 128
+#define VECTORSIZE 16
+#endif
+
 /*
  * ICC and MSVC don't break out POPCNT or BMI/2 as separate pre-def macros
  */