diff --git a/src/libvlr/vlr_auth_fsm.h b/src/libvlr/vlr_auth_fsm.h
index 1f2cb4969..f3925fda9 100644
--- a/src/libvlr/vlr_auth_fsm.h
+++ b/src/libvlr/vlr_auth_fsm.h
@@ -27,7 +27,7 @@ enum vlr_fsm_auth_event {
 	VLR_AUTH_E_MS_ID_IMSI,
 };
 
-struct osmo_fsm vlr_auth_fsm;
+extern struct osmo_fsm vlr_auth_fsm;
 
 struct osmo_fsm_inst *auth_fsm_start(struct vlr_subscr *vsub,
 				     uint32_t log_level,