diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index 690ca261..c4e03041 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -818,11 +818,11 @@ struct uint128_wrapper {
 };
 
 // Compilers should be able to optimize this into the ror instruction.
-inline uint32_t rotr(uint32_t n, uint32_t r) noexcept {
+FMT_CONSTEXPR inline uint32_t rotr(uint32_t n, uint32_t r) noexcept {
   r &= 31;
   return (n >> r) | (n << (32 - r));
 }
-inline uint64_t rotr(uint64_t n, uint32_t r) noexcept {
+FMT_CONSTEXPR inline uint64_t rotr(uint64_t n, uint32_t r) noexcept {
   r &= 63;
   return (n >> r) | (n << (64 - r));
 }