diff --git a/include/fmt/format.h b/include/fmt/format.h
index 87fce444..2b7a933f 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -342,11 +342,13 @@ class uint128 {
     return {lhs.hi_ - (lhs.lo_ < rhs ? 1 : 0), lhs.lo_ - rhs};
   }
   FMT_CONSTEXPR auto operator>>(int shift) const -> uint128 {
+    if (shift == 0) return *this;
     if (shift == 64) return {0, hi_};
     if (shift > 64) return uint128(0, hi_) >> (shift - 64);
     return {hi_ >> shift, (hi_ << (64 - shift)) | (lo_ >> shift)};
   }
   FMT_CONSTEXPR auto operator<<(int shift) const -> uint128 {
+    if (shift == 0) return *this;
     if (shift == 64) return {lo_, 0};
     if (shift > 64) return uint128(lo_, 0) << (shift - 64);
     return {hi_ << shift | (lo_ >> (64 - shift)), (lo_ << shift)};
diff --git a/test/format-test.cc b/test/format-test.cc
index b99c7a79..c61d2ce4 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -76,6 +76,11 @@ TEST(uint128_test, shift) {
   EXPECT_EQ(static_cast<uint64_t>(n), 42);
   EXPECT_EQ(uint128(1) << 112, uint128(0x1000000000000, 0));
   EXPECT_EQ(uint128(0x1000000000000, 0) >> 112, uint128(1));
+  // FMT_CONSTEXPR turns an undefined shift into a compile error.
+  FMT_CONSTEXPR auto lshift = uint128(1, 2) << 0;
+  FMT_CONSTEXPR auto rshift = uint128(1, 2) >> 0;
+  EXPECT_EQ(lshift, uint128(1, 2));
+  EXPECT_EQ(rshift, uint128(1, 2));
 }
 
 TEST(uint128_test, minus) {