diff --git a/daemon/call.c b/daemon/call.c
index 912919197..586236a6b 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -2276,7 +2276,11 @@ done:
 int call_stream_address(char *o, struct packet_stream *ps, enum stream_address_format format, int *len) {
 	csa_func f;
 
+	o[0] = 0;
+	*len = 0;
 	ps = packet_stream_sink(ps);
+	if (!ps)
+		return -1;
 	f = __call_stream_address(ps, 0);
 	return f(o, ps, format, len);
 }
@@ -2284,7 +2288,11 @@ int call_stream_address(char *o, struct packet_stream *ps, enum stream_address_f
 int call_stream_address_alt(char *o, struct packet_stream *ps, enum stream_address_format format, int *len) {
 	csa_func f;
 
+	o[0] = 0;
+	*len = 0;
 	ps = packet_stream_sink(ps);
+	if (!ps)
+		return -1;
 	f = __call_stream_address(ps, 1);
 	return f ? f(o, ps, format, len) : -1;
 }