diff --git a/src/or/scheduler.c b/src/or/scheduler.c
index 8a6620b049..367480cb31 100644
--- a/src/or/scheduler.c
+++ b/src/or/scheduler.c
@@ -275,8 +275,8 @@ scheduler_channel_doesnt_want_writes,(channel_t *chan))
 
 /** Mark a channel as having waiting cells */
 
-void
-scheduler_channel_has_waiting_cells(channel_t *chan)
+MOCK_IMPL(void,
+scheduler_channel_has_waiting_cells,(channel_t *chan))
 {
   int became_pending = 0;
 
diff --git a/src/or/scheduler.h b/src/or/scheduler.h
index 0752ae0760..7f59ec45d0 100644
--- a/src/or/scheduler.h
+++ b/src/or/scheduler.h
@@ -22,7 +22,7 @@ void scheduler_run(void);
 
 /* Mark channels as having cells or wanting/not wanting writes */
 MOCK_DECL(void,scheduler_channel_doesnt_want_writes,(channel_t *chan));
-void scheduler_channel_has_waiting_cells(channel_t *chan);
+MOCK_DECL(void,scheduler_channel_has_waiting_cells,(channel_t *chan));
 void scheduler_channel_wants_writes(channel_t *chan);
 
 /* Notify the scheduler of a channel being closed */