diff --git a/flang/runtime/format-implementation.h b/flang/runtime/format-implementation.h
index c54ac062c7bea..9c342db2e19a2 100644
--- a/flang/runtime/format-implementation.h
+++ b/flang/runtime/format-implementation.h
@@ -85,8 +85,9 @@ int FormatControl<CONTEXT>::GetIntField(
     ch = PeekNext();
   }
   while (ch >= '0' && ch <= '9') {
-    if (result >
-        std::numeric_limits<int>::max() / 10 - (static_cast<int>(ch) - '0')) {
+    constexpr int tenth{std::numeric_limits<int>::max() / 10};
+    if (result > tenth ||
+        ch - '0' > std::numeric_limits<int>::max() - 10 * result) {
       handler.SignalError(
           IostatErrorInFormat, "FORMAT integer field out of range");
       if (hadError) {