diff --git a/ArduCopter/GCS_Mavlink.pde b/ArduCopter/GCS_Mavlink.pde
index 15a087db90..0089118281 100644
--- a/ArduCopter/GCS_Mavlink.pde
+++ b/ArduCopter/GCS_Mavlink.pde
@@ -1955,7 +1955,7 @@ GCS_MAVLINK::queued_waypoint_send()
  MAVLink to process packets while waiting for the initialisation to
  complete
 */
-static void mavlink_delay(uint32_t t)
+static void mavlink_delay(unsigned long t)
 {
     uint32_t tstart;
     static uint32_t last_1hz, last_50hz, last_5s;
diff --git a/ArduPlane/GCS_Mavlink.pde b/ArduPlane/GCS_Mavlink.pde
index 57506d40f1..b16e04acf9 100644
--- a/ArduPlane/GCS_Mavlink.pde
+++ b/ArduPlane/GCS_Mavlink.pde
@@ -1963,7 +1963,7 @@ GCS_MAVLINK::queued_waypoint_send()
  MAVLink to process packets while waiting for the initialisation to
  complete
 */
-static void mavlink_delay(uint32_t t)
+static void mavlink_delay(unsigned long t)
 {
     uint32_t tstart;
     static uint32_t last_1hz, last_50hz, last_5s;