@@ -1471,11 +1471,11 @@
 				      withString: @"\\\n"];
 
 		if (options & OF_JSON_REPRESENTATION_IDENTIFIER) {
 			const char *cString = [self UTF8String];
 
-			if ((!isalpha(cString[0]) && cString[0] != '_' &&
+			if ((!isalpha((int)cString[0]) && cString[0] != '_' &&
 			    cString[0] != '$') ||
 			    strpbrk(cString, " \n\r\t\b\f\\\"'") != NULL) {
 				[JSON prependString: @"\""];
 				[JSON appendString: @"\""];
 			}