diff --git a/arch/sim/src/up_oneshot.c b/arch/sim/src/up_oneshot.c
index 8f4a368333e..cef9c9b2ea4 100644
--- a/arch/sim/src/up_oneshot.c
+++ b/arch/sim/src/up_oneshot.c
@@ -77,7 +77,7 @@ struct sim_oneshot_lowerhalf_s
  * Private Function Prototypes
  ****************************************************************************/
 
-static void sim_oneshot_handler(void *arg);
+static void sim_oneshot_handler(int argc, wdparm_t arg1, ...);
 
 static int sim_max_delay(FAR struct oneshot_lowerhalf_s *lower,
                          FAR struct timespec *ts);
@@ -119,14 +119,14 @@ static const struct oneshot_operations_s g_oneshot_ops =
  *
  ****************************************************************************/
 
-static void sim_oneshot_handler(void *arg)
+static void sim_oneshot_handler(int argc, wdparm_t arg1, ...)
 {
   FAR struct sim_oneshot_lowerhalf_s *priv =
-    (FAR struct sim_oneshot_lowerhalf_s *)arg;
+    (FAR struct sim_oneshot_lowerhalf_s *)arg1;
   oneshot_callback_t callback;
   FAR void *cbarg;
 
-  DEBUGASSERT(priv != NULL);
+  DEBUGASSERT(argc == 1 && priv != NULL);
 
   /* Perhaps the callback was nullified in a race condition with
    * sim_cancel?
diff --git a/drivers/timers/oneshot.c b/drivers/timers/oneshot.c
index 975f83bba2b..518071d19db 100644
--- a/drivers/timers/oneshot.c
+++ b/drivers/timers/oneshot.c
@@ -239,9 +239,8 @@ static int oneshot_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
       return ret;
     }
 
-  /* Handle built-in ioctl commands */
+  /* Handle oneshot timer ioctl commands */
 
-  ret = -EINVAL;
   switch (cmd)
     {
       /* OSIOC_MAXDELAY - Return the maximum delay that can be supported
@@ -286,7 +285,7 @@ static int oneshot_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 
           /* Start the oneshot timer */
 
-          ret = ONESHOT_START(priv->od_lower, oneshot_callback, start->arg,
+          ret = ONESHOT_START(priv->od_lower, oneshot_callback, priv,
                               &start->ts);
         }
         break;