diff --git a/libasn1fix/asn1fix.c b/libasn1fix/asn1fix.c
index 0511868..8d2317f 100644
--- a/libasn1fix/asn1fix.c
+++ b/libasn1fix/asn1fix.c
@@ -385,7 +385,7 @@
 	}
 
 	/* Check identifier distinctness */
-	ret = asn1f_check_unique_expr(arg, NULL);
+	ret = asn1f_check_unique_expr(arg);
 	RET2RVAL(ret, rvalue);
 
 	/* Fix extensibility */