diff --git a/include/intx/int128.hpp b/include/intx/int128.hpp
index 5132e819..7abafc40 100644
--- a/include/intx/int128.hpp
+++ b/include/intx/int128.hpp
@@ -374,6 +374,7 @@ inline constexpr uint128 umul(uint64_t x, uint64_t y) noexcept
     #pragma GCC diagnostic pop
 #endif
 
+    // LCOV_EXCL_START
     // Portable full unsigned multiplication 64 x 64 -> 128.
     uint64_t xl = x & 0xffffffff;
     uint64_t xh = x >> 32;
@@ -391,6 +392,7 @@ inline constexpr uint128 umul(uint64_t x, uint64_t y) noexcept
     uint64_t lo = (u2 << 32) | (t0 & 0xffffffff);
     uint64_t hi = t3 + (u2 >> 32) + (u1 >> 32);
     return {hi, lo};
+    // LCOV_EXCL_STOP
 }
 
 inline uint128 operator*(uint128 x, uint128 y) noexcept