diff --git a/src/data-device.c b/src/data-device.c
index 797fdd73..03997f19 100644
--- a/src/data-device.c
+++ b/src/data-device.c
@@ -248,7 +248,7 @@ data_device_end_drag_grab(struct wl_input_device *device, uint32_t time)
 
 static void
 drag_grab_button(struct wl_pointer_grab *grab,
-		 uint32_t time, int32_t button, int32_t state)
+		 uint32_t time, uint32_t button, int32_t state)
 {
 	struct wl_input_device *device =
 		container_of(grab, struct wl_input_device, drag_grab);
diff --git a/src/wayland-server.c b/src/wayland-server.c
index 0c0d0288..8c7323d2 100644
--- a/src/wayland-server.c
+++ b/src/wayland-server.c
@@ -474,7 +474,7 @@ default_grab_motion(struct wl_pointer_grab *grab,
 
 static void
 default_grab_button(struct wl_pointer_grab *grab,
-		    uint32_t time, int32_t button, int32_t state)
+		    uint32_t time, uint32_t button, int32_t state)
 {
 	struct wl_input_device *device = grab->input_device;
 	struct wl_resource *resource;
diff --git a/src/wayland-server.h b/src/wayland-server.h
index 1a0878b6..2e522446 100644
--- a/src/wayland-server.h
+++ b/src/wayland-server.h
@@ -143,7 +143,7 @@ struct wl_pointer_grab_interface {
 	void (*motion)(struct wl_pointer_grab *grab,
 		       uint32_t time, int32_t x, int32_t y);
 	void (*button)(struct wl_pointer_grab *grab,
-		       uint32_t time, int32_t button, int32_t state);
+		       uint32_t time, uint32_t button, int32_t state);
 };
 
 struct wl_pointer_grab {