diff --git a/include/fmt/format.h b/include/fmt/format.h
index ca26e772..845e7c44 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -193,7 +193,7 @@ namespace detail {
 #  ifndef __clang__
 #    pragma intrinsic(_BitScanReverse)
 #  endif
-inline uint32_t clz(uint32_t x) {
+inline int clz(uint32_t x) {
   unsigned long r = 0;
   _BitScanReverse(&r, x);
 
@@ -202,7 +202,7 @@ inline uint32_t clz(uint32_t x) {
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
   FMT_SUPPRESS_MSC_WARNING(6102)
-  return 31 - r;
+  return 31 - static_cast<int>(r);
 }
 #  define FMT_BUILTIN_CLZ(n) detail::clz(n)
 
@@ -210,7 +210,7 @@ inline uint32_t clz(uint32_t x) {
 #    pragma intrinsic(_BitScanReverse64)
 #  endif
 
-inline uint32_t clzll(uint64_t x) {
+inline int clzll(uint64_t x) {
   unsigned long r = 0;
 #  ifdef _WIN64
   _BitScanReverse64(&r, x);
@@ -227,7 +227,7 @@ inline uint32_t clzll(uint64_t x) {
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
   FMT_SUPPRESS_MSC_WARNING(6102)
-  return 63 - r;
+  return 63 - static_cast<int>(r);
 }
 #  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
 }  // namespace detail