diff --git a/include/dwarfs/nilsimsa.h b/include/dwarfs/nilsimsa.h
index 13d63713..d6bae789 100644
--- a/include/dwarfs/nilsimsa.h
+++ b/include/dwarfs/nilsimsa.h
@@ -26,17 +26,15 @@
 #include <memory>
 #include <type_traits>
 
+#include <folly/lang/Bits.h>
+
 #include "dwarfs/compiler.h"
 
 #define DWARFS_NILSIMSA_SIMILARITY(r, a, b)                                    \
   do {                                                                         \
     int bits = 0;                                                              \
     for (int i = 0; i < 4; ++i) {                                              \
-      if constexpr (std::is_same_v<unsigned long, uint64_t>) {                 \
-        bits += __builtin_popcountl(a[i] ^ b[i]);                              \
-      } else if constexpr (std::is_same_v<unsigned long long, uint64_t>) {     \
-        bits += __builtin_popcountll(a[i] ^ b[i]);                             \
-      }                                                                        \
+      bits += folly::popcount(a[i] ^ b[i]);                                    \
     }                                                                          \
     r 255 - bits;                                                              \
   } while (false)