diff --git a/openbsc/include/openbsc/tlv.h b/openbsc/include/openbsc/tlv.h
index e970ce4..c90643e 100644
--- a/openbsc/include/openbsc/tlv.h
+++ b/openbsc/include/openbsc/tlv.h
@@ -185,6 +185,7 @@
 };
 
 enum tlv_type {
+	TLV_TYPE_NONE,
 	TLV_TYPE_FIXED,
 	TLV_TYPE_T,
 	TLV_TYPE_TV,
@@ -213,6 +214,8 @@
                   const u_int8_t *buf, int buf_len);
 int tlv_parse(struct tlv_parsed *dec, const struct tlv_definition *def,
 	      const u_int8_t *buf, int buf_len, u_int8_t lv_tag, u_int8_t lv_tag2);
+/* take a master (src) tlvdev and fill up all empty slots in 'dst' */
+void tlv_def_patch(struct tlv_definition *dst, const struct tlv_definition *src);
 
 #define TLVP_PRESENT(x, y)	((x)->lv[y].val)
 #define TLVP_LEN(x, y)		(x)->lv[y].len
diff --git a/openbsc/src/tlv_parser.c b/openbsc/src/tlv_parser.c
index fd0045f..13ca7b1 100644
--- a/openbsc/src/tlv_parser.c
+++ b/openbsc/src/tlv_parser.c
@@ -149,6 +149,19 @@
 	return num_parsed;
 }
 
+/* take a master (src) tlvdev and fill up all empty slots in 'dst' */
+void tlv_def_patch(struct tlv_definition *dst, const struct tlv_definition *src)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(dst->def); i++) {
+		if (src->def[i].type == TLV_TYPE_NONE)
+			continue;
+		if (dst->def[i].type == TLV_TYPE_NONE)
+			dst->def[i] = src->def[i];
+	}
+}
+
 static __attribute__((constructor)) void on_dso_load_tlv(void)
 {
 	int i;