diff --git a/clutter/clutter/clutter-input-device-tool.c b/clutter/clutter/clutter-input-device-tool.c
index 11c72ad2b..516955515 100644
--- a/clutter/clutter/clutter-input-device-tool.c
+++ b/clutter/clutter/clutter-input-device-tool.c
@@ -136,7 +136,7 @@ clutter_input_device_tool_init (ClutterInputDeviceTool *tool)
  *
  * Since: 1.28
  **/
-guint
+guint64
 clutter_input_device_tool_get_serial (ClutterInputDeviceTool *tool)
 {
   ClutterInputDeviceToolPrivate *priv;
diff --git a/clutter/clutter/clutter-input-device-tool.h b/clutter/clutter/clutter-input-device-tool.h
index 8795d058d..097dec83b 100644
--- a/clutter/clutter/clutter-input-device-tool.h
+++ b/clutter/clutter/clutter-input-device-tool.h
@@ -56,7 +56,7 @@ CLUTTER_AVAILABLE_IN_ALL
 GType                      clutter_input_device_tool_get_type (void) G_GNUC_CONST;
 
 CLUTTER_AVAILABLE_IN_ALL
-guint                      clutter_input_device_tool_get_serial    (ClutterInputDeviceTool *tool);
+guint64                    clutter_input_device_tool_get_serial    (ClutterInputDeviceTool *tool);
 
 CLUTTER_AVAILABLE_IN_ALL
 ClutterInputDeviceToolType clutter_input_device_tool_get_tool_type (ClutterInputDeviceTool *tool);