diff --git a/lib/asn1/gen_free.c b/lib/asn1/gen_free.c
index 115eb2ed6..aa323c0ad 100644
--- a/lib/asn1/gen_free.c
+++ b/lib/asn1/gen_free.c
@@ -127,14 +127,14 @@ free_type (const char *name, const Type *t, int preserve)
     case TSequenceOf: {
 	char *n;
 
-	fprintf (codefile, "while((%s)->len){\n", name);
+	fprintf (codefile, "if ((%s)->val)\nwhile((%s)->len){\n", name, name);
 	if (asprintf (&n, "&(%s)->val[(%s)->len-1]", name, name) < 0 || n == NULL)
 	    errx(1, "malloc");
 	free_type(n, t->subtype, FALSE);
 	fprintf(codefile,
 		"(%s)->len--;\n"
-		"}\n",
-		name);
+		"} else (%s)->len = 0;\n",
+		name, name);
 	fprintf(codefile,
 		"free((%s)->val);\n"
 		"(%s)->val = NULL;\n", name, name);