diff --git a/epan/packet.c b/epan/packet.c
index 1ad0320..179011e 100644
--- a/epan/packet.c
+++ b/epan/packet.c
@@ -1266,6 +1266,7 @@ dissector_get_string_handle(dissector_table_t sub_dissectors,
 {
 	dtbl_entry_t *dtbl_entry;
 
+	if (!string) return 0;
 	dtbl_entry = find_string_dtbl_entry(sub_dissectors, string);
 	if (dtbl_entry != NULL)
 		return dtbl_entry->current;