diff --git a/openbsc/src/e1_input.c b/openbsc/src/e1_input.c
index 8dce132..a17ae41 100644
--- a/openbsc/src/e1_input.c
+++ b/openbsc/src/e1_input.c
@@ -302,7 +302,7 @@
 
 	switch (type) {
 	case E1INP_TS_TYPE_SIGN:
-		if (line->driver)
+		if (line && line->driver)
 			ts->sign.delay = line->driver->default_delay;
 		else
 			ts->sign.delay = 100000;