diff --git a/ShellPkg/Library/UefiShellLib/UefiShellLib.c b/ShellPkg/Library/UefiShellLib/UefiShellLib.c
index e30e5c7dd1..ad8e80ea83 100644
--- a/ShellPkg/Library/UefiShellLib/UefiShellLib.c
+++ b/ShellPkg/Library/UefiShellLib/UefiShellLib.c
@@ -1903,7 +1903,7 @@ InternalIsFlag (
   //
   // If we accept numbers then dont return TRUE. (they will be values)
   //
-  if (((Name[0] == L'-' || Name[0] == L'+') && ShellIsHexaDecimalDigitCharacter(Name[1])) && AlwaysAllowNumbers) {
+  if (((Name[0] == L'-' || Name[0] == L'+') && InternalShellIsHexOrDecimalNumber(Name+1, FALSE, FALSE)) && AlwaysAllowNumbers) {
     return (FALSE);
   }