diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index 7fc737b..9bf1d7f 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -265,7 +265,7 @@
 			 gprs_ns2_fr_nsvc_dlci(nsvc));
 		break;
 	default:
-		buf[0] = '\0';
+		snprintf(buf, buf_len, "unknown)");
 		break;
 	}