diff --git a/sqlite-vec.c b/sqlite-vec.c
index 7af3b6a7..d329d38c 100644
--- a/sqlite-vec.c
+++ b/sqlite-vec.c
@@ -782,7 +782,11 @@ static unsigned int __builtin_popcountl(unsigned int x) {
 }
 #else
 #include <intrin.h>
+#ifdef _WIN64
 #define __builtin_popcountl __popcnt64
+#else
+static unsigned int __builtin_popcountl(u64 n) { return __popcnt((u32)n) + __popcnt((u32)(n >> 32)); }
+#endif
 #endif
 #endif