diff --git a/build_tools/build_detect_platform b/build_tools/build_detect_platform
index 440c6a5e39f..ff95c75f06b 100755
--- a/build_tools/build_detect_platform
+++ b/build_tools/build_detect_platform
@@ -456,7 +456,7 @@ elif test -z "$PORTABLE"; then
   fi
 fi
 
-$CXX $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
+$CXX $PLATFORM_CXXFLAGS $COMMON_FLAGS -x c++ - -o /dev/null 2>/dev/null <<EOF
   #include <cstdint>
   #include <nmmintrin.h>
   int main() {
diff --git a/util/crc32c.cc b/util/crc32c.cc
index ae36f82305b..0246ce093e6 100644
--- a/util/crc32c.cc
+++ b/util/crc32c.cc
@@ -313,6 +313,15 @@ static inline void Slow_CRC32(uint64_t* l, uint8_t const **p) {
   table0_[c >> 24];
 }
 
+#if defined(HAVE_SSE42) && defined(__GNUC__)
+#if defined(__clang__)
+#if __has_cpp_attribute(gnu::target)
+__attribute__ ((target ("sse4.2")))
+#endif
+#else  // gcc supports this since 4.4
+__attribute__ ((target ("sse4.2")))
+#endif
+#endif
 static inline void Fast_CRC32(uint64_t* l, uint8_t const **p) {
 #ifndef HAVE_SSE42
   Slow_CRC32(l, p);
@@ -376,8 +385,7 @@ static bool isSSE42() {
   return false;
 #elif defined(__GNUC__) && defined(__x86_64__) && !defined(IOS_CROSS_COMPILE)
   uint32_t c_;
-  uint32_t d_;
-  __asm__("cpuid" : "=c"(c_), "=d"(d_) : "a"(1) : "ebx");
+  __asm__("cpuid" : "=c"(c_) : "a"(1) : "ebx", "edx");
   return c_ & (1U << 20);  // copied from CpuId.h in Folly.
 #elif defined(_WIN64)
   int info[4];
@@ -398,7 +406,7 @@ bool IsFastCrc32Supported() {
   return isSSE42();
 }
 
-Function ChosenExtend = Choose_Extend();
+static Function ChosenExtend = Choose_Extend();
 
 uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
   return ChosenExtend(crc, buf, size);