diff --git a/artiq/runtime/dds.c b/artiq/runtime/dds.c
index ea6d650db..18cb11cec 100644
--- a/artiq/runtime/dds.c
+++ b/artiq/runtime/dds.c
@@ -85,7 +85,7 @@ void dds_init(long long int timestamp, int bus_channel, int channel)
 static unsigned int continuous_phase_comp[CONFIG_DDS_CHANNEL_COUNT];
 
 static void dds_set_one(long long int now, long long int ref_time,
-    unsigned int bus_channel, unsigned int channel,
+    int bus_channel, int channel,
     unsigned int ftw, unsigned int pow, int phase_mode, unsigned int amplitude)
 {
     unsigned int channel_enc;
diff --git a/artiq/runtime/dds.h b/artiq/runtime/dds.h
index 6d4e5d972..10fa3fffc 100644
--- a/artiq/runtime/dds.h
+++ b/artiq/runtime/dds.h
@@ -54,10 +54,10 @@ enum {
     PHASE_MODE_TRACKING = 2
 };
 
-void dds_init(long long int timestamp, int channel);
+void dds_init(long long int timestamp, int bus_channel, int channel);
 void dds_batch_enter(long long int timestamp);
 void dds_batch_exit(void);
-void dds_set(long long int timestamp, int channel,
+void dds_set(long long int timestamp, int bus_channel, int channel,
     unsigned int ftw, unsigned int pow, int phase_mode, unsigned int amplitude);
 
 #endif /* __DDS_H */