diff --git a/src/cmd/internal/obj/s390x/condition_code.go b/src/cmd/internal/obj/s390x/condition_code.go
index f498fd6f77..3330d1310d 100644
--- a/src/cmd/internal/obj/s390x/condition_code.go
+++ b/src/cmd/internal/obj/s390x/condition_code.go
@@ -122,7 +122,7 @@ func (c CCMask) String() string {
 	}
 
 	// invalid
-	return fmt.Sprintf("Invalid (%#x)", c)
+	return fmt.Sprintf("Invalid (%#x)", uint8(c))
 }
 
 func (CCMask) CanBeAnSSAAux() {}