diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index eae85ab6..52e83069 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -976,7 +976,8 @@ static inline size_t mi_ctz_generic32(uint32_t x) {
     31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
   };
   if (x==0) return 32;
-  return debruijn[(uint32_t)((x & -(int32_t)x) * (uint32_t)(0x077CB531U)) >> 27];
+  return debruijn[(((x & -(int32_t)x) * 0x077CB531U) >> 27) & 31];
+
 }
 
 static inline size_t mi_clz_generic32(uint32_t x) {
@@ -991,7 +992,8 @@ static inline size_t mi_clz_generic32(uint32_t x) {
   x |= x >> 4;
   x |= x >> 8;
   x |= x >> 16;
-  return debruijn[(uint32_t)(x * (uint32_t)(0x07C4ACDDU)) >> 27];
+  return debruijn[((x * 0x07C4ACDDU) >> 27) & 31];
+
 }
 
 static inline size_t mi_ctz(size_t x) {