diff --git a/include/osmocom/gsm/protocol/gsm_12_21.h b/include/osmocom/gsm/protocol/gsm_12_21.h
index d6e8c11..40237cb 100644
--- a/include/osmocom/gsm/protocol/gsm_12_21.h
+++ b/include/osmocom/gsm/protocol/gsm_12_21.h
@@ -595,6 +595,7 @@
 };
 
 extern const struct value_string abis_nm_pcause_type_names[];
+extern const struct value_string abis_nm_att_names[];
 
 /*! \brief NACK causes (Section 9.4.36) */
 enum abis_nm_nack_cause {