diff --git a/src/external/sinfl.h b/src/external/sinfl.h
index 591fcf1cb..38564f701 100644
--- a/src/external/sinfl.h
+++ b/src/external/sinfl.h
@@ -172,9 +172,9 @@ extern int zsinflate(void *out, int cap, const void *in, int size);
 static int
 sinfl_bsr(unsigned n) {
 #ifdef _MSC_VER
-  unsigned long r = 0;
-  _BitScanReverse(&r, n);
-  return int(r);
+  unsigned long uln = 0;
+  _BitScanReverse(&uln, n);
+  return int(uln);
 #else // defined(__GNUC__) || defined(__clang__) || defined(__TINYC__)
   return 31 - __builtin_clz(n);
 #endif