diff --git a/compiler-rt/lib/builtins/int_mulo_impl.inc b/compiler-rt/lib/builtins/int_mulo_impl.inc
--- a/compiler-rt/lib/builtins/int_mulo_impl.inc
+++ b/compiler-rt/lib/builtins/int_mulo_impl.inc
@@ -21,7 +21,7 @@
   const fixint_t MIN = (fixint_t)((fixuint_t)1 << (N - 1));
   const fixint_t MAX = ~MIN;
   *overflow = 0;
-  fixint_t result = a * b;
+  fixint_t result = (fixuint_t)a * b;
   if (a == MIN) {
     if (b != 0 && b != 1)
       *overflow = 1;