diff --git a/util/crc32c.cc b/util/crc32c.cc
index 5008dddee..ff7991753 100644
--- a/util/crc32c.cc
+++ b/util/crc32c.cc
@@ -291,9 +291,11 @@ static inline uint32_t LE_LOAD32(const uint8_t *p) {
   return DecodeFixed32(reinterpret_cast<const char*>(p));
 }
 
+#ifdef __SSE4_2__
 static inline uint64_t LE_LOAD64(const uint8_t *p) {
   return DecodeFixed64(reinterpret_cast<const char*>(p));
 }
+#else
 
 static inline void Slow_CRC32(uint64_t* l, uint8_t const **p) {
   uint32_t c = *l ^ LE_LOAD32(*p);