--- a/jack.c
+++ b/jack.c
@@ -107,7 +107,7 @@ jo_data;
 static int init_resampler();
 static int init_channels();
 static int connect_ports();
-static int process_source_data();
+static int process_source_data(receiver_data_t *data);
 
 // JACK realtime process callback
 int jack_process(jack_nframes_t nframes, void *arg);