diff --git a/include/wlr/types/wlr_gtk_primary_selection.h b/include/wlr/types/wlr_gtk_primary_selection.h
index ed025869..cbf29088 100644
--- a/include/wlr/types/wlr_gtk_primary_selection.h
+++ b/include/wlr/types/wlr_gtk_primary_selection.h
@@ -45,18 +45,24 @@ struct wlr_gtk_primary_selection_device {
 	void *data;
 };
 
+/**
+ * A data source implementation. Only the `send` function is mandatory.
+ */
+struct wlr_gtk_primary_selection_source_impl {
+	void (*send)(struct wlr_gtk_primary_selection_source *source,
+		const char *mime_type, int fd);
+	void (*destroy)(struct wlr_gtk_primary_selection_source *source);
+};
+
 /**
  * A source is the sending side of a selection.
  */
 struct wlr_gtk_primary_selection_source {
+	const struct wlr_gtk_primary_selection_source_impl *impl;
+
 	// source metadata
 	struct wl_array mime_types;
 
-	// source implementation
-	void (*send)(struct wlr_gtk_primary_selection_source *source,
-		const char *mime_type, int32_t fd);
-	void (*cancel)(struct wlr_gtk_primary_selection_source *source);
-
 	struct {
 		struct wl_signal destroy;
 	} events;
@@ -75,8 +81,12 @@ void wlr_gtk_primary_selection_device_manager_set_selection(
 	struct wlr_gtk_primary_selection_source *source);
 
 void wlr_gtk_primary_selection_source_init(
+	struct wlr_gtk_primary_selection_source *source,
+	const struct wlr_gtk_primary_selection_source_impl *impl);
+void wlr_gtk_primary_selection_source_destroy(
 	struct wlr_gtk_primary_selection_source *source);
-void wlr_gtk_primary_selection_source_finish(
-	struct wlr_gtk_primary_selection_source *source);
+void wlr_gtk_primary_selection_source_send(
+	struct wlr_gtk_primary_selection_source *source, const char *mime_type,
+	int fd);
 
 #endif
diff --git a/types/wlr_gtk_primary_selection.c b/types/wlr_gtk_primary_selection.c
index 9a8848d6..5a31d242 100644
--- a/types/wlr_gtk_primary_selection.c
+++ b/types/wlr_gtk_primary_selection.c
@@ -29,7 +29,7 @@ static void offer_handle_receive(struct wl_client *client,
 		return;
 	}
 
-	device->source->send(device->source, mime_type, fd);
+	wlr_gtk_primary_selection_source_send(device->source, mime_type, fd);
 }
 
 static void offer_handle_destroy(struct wl_client *client,
@@ -99,19 +99,26 @@ struct client_data_source {
 
 static void client_source_send(
 		struct wlr_gtk_primary_selection_source *wlr_source,
-		const char *mime_type, int32_t fd) {
+		const char *mime_type, int fd) {
 	struct client_data_source *source = (struct client_data_source *)wlr_source;
 	gtk_primary_selection_source_send_send(source->resource, mime_type, fd);
 	close(fd);
 }
 
-static void client_source_cancel(
+static void client_source_destroy(
 		struct wlr_gtk_primary_selection_source *wlr_source) {
 	struct client_data_source *source = (struct client_data_source *)wlr_source;
 	gtk_primary_selection_source_send_cancelled(source->resource);
-	// TODO: make the source resource inert
+	// Make the source resource inert
+	wl_resource_set_user_data(source->resource, NULL);
+	free(source);
 }
 
+static const struct wlr_gtk_primary_selection_source_impl client_source_impl = {
+	.send = client_source_send,
+	.destroy = client_source_destroy,
+};
+
 static const struct gtk_primary_selection_source_interface source_impl;
 
 static struct client_data_source *client_data_source_from_resource(
@@ -125,6 +132,9 @@ static void source_handle_offer(struct wl_client *client,
 		struct wl_resource *resource, const char *mime_type) {
 	struct client_data_source *source =
 		client_data_source_from_resource(resource);
+	if (source == NULL) {
+		return;
+	}
 
 	char **p = wl_array_add(&source->source.mime_types, sizeof(*p));
 	if (p) {
@@ -151,8 +161,10 @@ static const struct gtk_primary_selection_source_interface source_impl = {
 static void source_resource_handle_destroy(struct wl_resource *resource) {
 	struct client_data_source *source =
 		client_data_source_from_resource(resource);
-	wlr_gtk_primary_selection_source_finish(&source->source);
-	free(source);
+	if (source == NULL) {
+		return;
+	}
+	wlr_gtk_primary_selection_source_destroy(&source->source);
 }
 
 
@@ -174,15 +186,20 @@ static void device_handle_set_selection(struct wl_client *client,
 		return;
 	}
 
-	struct client_data_source *source = NULL;
+	struct client_data_source *client_source = NULL;
 	if (source_resource != NULL) {
-		source = client_data_source_from_resource(source_resource);
+		client_source = client_data_source_from_resource(source_resource);
+	}
+
+	struct wlr_gtk_primary_selection_source *source = NULL;
+	if (client_source != NULL) {
+		source = &client_source->source;
 	}
 
 	// TODO: improve serial checking
 	struct wlr_seat *seat = device->seat;
 	wlr_gtk_primary_selection_device_manager_set_selection(device->manager,
-		seat, &source->source);
+		seat, source);
 }
 
 static void device_handle_destroy(struct wl_client *client,
@@ -230,14 +247,9 @@ static void device_handle_source_destroy(struct wl_listener *listener,
 static void device_set_selection(
 		struct wlr_gtk_primary_selection_device *device,
 		struct wlr_gtk_primary_selection_source *source) {
-	if (source != NULL) {
-		assert(source->send);
-		assert(source->cancel);
-	}
-
 	if (device->source != NULL) {
 		wl_list_remove(&device->source_destroy.link);
-		device->source->cancel(device->source);
+		wlr_gtk_primary_selection_source_destroy(device->source);
 		device->source = NULL;
 	}
 
@@ -328,7 +340,7 @@ static void device_destroy(struct wlr_gtk_primary_selection_device *device) {
 	wl_list_remove(&device->seat_focus_change.link);
 	if (device->source != NULL) {
 		wl_list_remove(&device->source_destroy.link);
-		device->source->cancel(device->source);
+		wlr_gtk_primary_selection_source_destroy(device->source);
 	}
 	struct wl_resource *resource, *resource_tmp;
 	wl_resource_for_each_safe(resource, resource_tmp, &device->offers) {
@@ -356,27 +368,6 @@ struct wlr_gtk_primary_selection_device_manager *manager_from_resource(
 	return wl_resource_get_user_data(resource);
 }
 
-void wlr_gtk_primary_selection_source_init(
-		struct wlr_gtk_primary_selection_source *source) {
-	wl_array_init(&source->mime_types);
-	wl_signal_init(&source->events.destroy);
-}
-
-void wlr_gtk_primary_selection_source_finish(
-		struct wlr_gtk_primary_selection_source *source) {
-	if (source == NULL) {
-		return;
-	}
-
-	wlr_signal_emit_safe(&source->events.destroy, source);
-
-	char **p;
-	wl_array_for_each(p, &source->mime_types) {
-		free(*p);
-	}
-	wl_array_release(&source->mime_types);
-}
-
 static void device_manager_handle_create_source(struct wl_client *client,
 		struct wl_resource *manager_resource, uint32_t id) {
 	struct client_data_source *source =
@@ -385,7 +376,7 @@ static void device_manager_handle_create_source(struct wl_client *client,
 		wl_client_post_no_memory(client);
 		return;
 	}
-	wlr_gtk_primary_selection_source_init(&source->source);
+	wlr_gtk_primary_selection_source_init(&source->source, &client_source_impl);
 
 	uint32_t version = wl_resource_get_version(manager_resource);
 	source->resource = wl_resource_create(client,
@@ -397,9 +388,6 @@ static void device_manager_handle_create_source(struct wl_client *client,
 	}
 	wl_resource_set_implementation(source->resource, &source_impl, source,
 		source_resource_handle_destroy);
-
-	source->source.send = client_source_send;
-	source->source.cancel = client_source_cancel;
 }
 
 void device_manager_handle_get_device(struct wl_client *client,
@@ -525,3 +513,40 @@ void wlr_gtk_primary_selection_device_manager_destroy(
 	wl_global_destroy(manager->global);
 	free(manager);
 }
+
+
+void wlr_gtk_primary_selection_source_init(
+		struct wlr_gtk_primary_selection_source *source,
+		const struct wlr_gtk_primary_selection_source_impl *impl) {
+	assert(impl->send);
+	wl_array_init(&source->mime_types);
+	wl_signal_init(&source->events.destroy);
+	source->impl = impl;
+}
+
+void wlr_gtk_primary_selection_source_destroy(
+		struct wlr_gtk_primary_selection_source *source) {
+	if (source == NULL) {
+		return;
+	}
+
+	wlr_signal_emit_safe(&source->events.destroy, source);
+
+	char **p;
+	wl_array_for_each(p, &source->mime_types) {
+		free(*p);
+	}
+	wl_array_release(&source->mime_types);
+
+	if (source->impl->destroy) {
+		source->impl->destroy(source);
+	} else {
+		free(source);
+	}
+}
+
+void wlr_gtk_primary_selection_source_send(
+		struct wlr_gtk_primary_selection_source *source, const char *mime_type,
+		int32_t fd) {
+	source->impl->send(source, mime_type, fd);
+}
diff --git a/xwayland/selection/incoming.c b/xwayland/selection/incoming.c
index 0fe759a0..3342a761 100644
--- a/xwayland/selection/incoming.c
+++ b/xwayland/selection/incoming.c
@@ -137,7 +137,7 @@ static void xwm_selection_get_data(struct wlr_xwm_selection *selection) {
 
 static void source_send(struct wlr_xwm_selection *selection,
 		struct wl_array *mime_types, struct wl_array *mime_types_atoms,
-		const char *requested_mime_type, int32_t fd) {
+		const char *requested_mime_type, int fd) {
 	struct wlr_xwm *xwm = selection->xwm;
 	struct wlr_xwm_selection_transfer *transfer = &selection->incoming;
 
@@ -222,17 +222,17 @@ struct x11_primary_selection_source {
 	struct wl_array mime_types_atoms;
 };
 
-static void primary_selection_source_cancel(
-	struct wlr_gtk_primary_selection_source *wlr_source);
+static const struct wlr_gtk_primary_selection_source_impl
+	primary_selection_source_impl;
 
 bool primary_selection_source_is_xwayland(
 		struct wlr_gtk_primary_selection_source *wlr_source) {
-	return wlr_source->cancel == primary_selection_source_cancel;
+	return wlr_source->impl == &primary_selection_source_impl;
 }
 
 static void primary_selection_source_send(
-		struct wlr_gtk_primary_selection_source *wlr_source, const char *mime_type,
-		int32_t fd) {
+		struct wlr_gtk_primary_selection_source *wlr_source,
+		const char *mime_type, int fd) {
 	struct x11_primary_selection_source *source =
 		(struct x11_primary_selection_source *)wlr_source;
 	struct wlr_xwm_selection *selection = source->selection;
@@ -241,15 +241,20 @@ static void primary_selection_source_send(
 		mime_type, fd);
 }
 
-static void primary_selection_source_cancel(
+static void primary_selection_source_destroy(
 		struct wlr_gtk_primary_selection_source *wlr_source) {
 	struct x11_primary_selection_source *source =
 		(struct x11_primary_selection_source *)wlr_source;
-	wlr_gtk_primary_selection_source_finish(&source->base);
 	wl_array_release(&source->mime_types_atoms);
 	free(source);
 }
 
+static const struct wlr_gtk_primary_selection_source_impl
+		primary_selection_source_impl = {
+	.send = primary_selection_source_send,
+	.destroy = primary_selection_source_destroy,
+};
+
 static bool source_get_targets(struct wlr_xwm_selection *selection,
 		struct wl_array *mime_types, struct wl_array *mime_types_atoms) {
 	struct wlr_xwm *xwm = selection->xwm;
@@ -356,9 +361,8 @@ static void xwm_selection_get_targets(struct wlr_xwm_selection *selection) {
 		if (source == NULL) {
 			return;
 		}
-		wlr_gtk_primary_selection_source_init(&source->base);
-		source->base.send = primary_selection_source_send;
-		source->base.cancel = primary_selection_source_cancel;
+		wlr_gtk_primary_selection_source_init(&source->base,
+			&primary_selection_source_impl);
 
 		source->selection = selection;
 		wl_array_init(&source->mime_types_atoms);
@@ -369,7 +373,7 @@ static void xwm_selection_get_targets(struct wlr_xwm_selection *selection) {
 			wlr_gtk_primary_selection_device_manager_set_selection(
 				xwm->xwayland->gtk_primary_selection, xwm->seat, &source->base);
 		} else {
-			source->base.cancel(&source->base);
+			wlr_gtk_primary_selection_source_destroy(&source->base);
 		}
 	} else if (selection == &xwm->dnd_selection) {
 		// TODO
diff --git a/xwayland/selection/outgoing.c b/xwayland/selection/outgoing.c
index b658ab52..1c994e18 100644
--- a/xwayland/selection/outgoing.c
+++ b/xwayland/selection/outgoing.c
@@ -198,7 +198,7 @@ static void xwm_selection_source_send(struct wlr_xwm_selection *selection,
 		struct wlr_gtk_primary_selection_source *source =
 			selection->xwm->seat->primary_selection_source;
 		if (source != NULL) {
-			source->send(source, mime_type, fd);
+			wlr_gtk_primary_selection_source_send(source, mime_type, fd);
 			return;
 		}
 	} else if (selection == &selection->xwm->dnd_selection) {