diff --git a/include/vk_mem_alloc.h b/include/vk_mem_alloc.h
index 97e321c..7544c53 100644
--- a/include/vk_mem_alloc.h
+++ b/include/vk_mem_alloc.h
@@ -3074,7 +3074,7 @@ static inline uint32_t VmaCountBitsSet(uint32_t v)
 
 static inline uint8_t VmaBitScanLSB(uint64_t mask)
 {
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && defined(_WIN64)
     unsigned long pos;
     if (_BitScanForward64(&pos, mask))
         return static_cast<uint8_t>(pos);
@@ -3108,7 +3108,7 @@ static inline uint8_t VmaBitScanLSB(uint32_t mask)
 
 static inline uint8_t VmaBitScanMSB(uint64_t mask)
 {
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && defined(_WIN64)
     unsigned long pos;
     if (_BitScanReverse64(&pos, mask))
         return static_cast<uint8_t>(pos);