diff --git a/dlls/oleaut32/typelib.c b/dlls/oleaut32/typelib.c
index 6b422b8ebe69362df132f9104e8616d8720329a5..8f4a3fb5604617eee78a53107447e32d7fd9a4f3 100644
--- a/dlls/oleaut32/typelib.c
+++ b/dlls/oleaut32/typelib.c
@@ -2916,7 +2916,7 @@ static SLTG_TypeInfoTail *SLTG_ProcessInterface(char *pBlk, ITypeInfoImpl *pTI,
 	        paramName = NULL;
 		HaveOffs = TRUE;
 	    }
-	    else if((unsigned char)paramName[-1] == 0xff)
+	    else if(paramName[-1] && !isalnum(paramName[-1]))
 	        HaveOffs = TRUE;
 
 	    pArg++;