diff --git a/openbsc/src/input/dahdi.c b/openbsc/src/input/dahdi.c
index e5d41e0..2fc99f5 100644
--- a/openbsc/src/input/dahdi.c
+++ b/openbsc/src/input/dahdi.c
@@ -403,8 +403,13 @@
 			fprintf(stderr, "Error setting bufinfo\n");
 			exit(-1);
 		}
+	} else {
+		int one = 1;
+		ioctl(fd, DAHDI_HDLCFCSMODE, &one);
+		/* we cannot reliably check for the ioctl return value here
+		 * as this command will fail if the slot _already_ was a
+		 * signalling slot before :( */
 	}
-
 }
 
 static int dahdi_e1_setup(struct e1inp_line *line)