diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index 4632019c..5ce967cb 100644
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -2813,7 +2813,7 @@ sna_output_add(struct sna *sna, int id, int serial)
 		}
 
 		possible_crtcs = enc.possible_crtcs;
-		assert(enc.encoder_id = compat_conn.conn.encoder_id);
+		assert(enc.encoder_id = compat_conn.conn.encoder_id || compat_conn.conn.encoder_id == 0);
 	} else {
 		DBG(("%s: unexpected number [%d] of encoders attached\n",
 		     __FUNCTION__, compat_conn.conn.count_encoders));