diff --git a/src/xwayland-unmanaged.c b/src/xwayland-unmanaged.c
index 8f8faf79..8c0067bd 100644
--- a/src/xwayland-unmanaged.c
+++ b/src/xwayland-unmanaged.c
@@ -144,7 +144,6 @@ unmanaged_handle_override_redirect(struct wl_listener *listener, void *data)
 		unmanaged_handle_unmap(&unmanaged->unmap, NULL);
 	}
 	unmanaged_handle_destroy(&unmanaged->destroy, NULL);
-	xsurface->data = NULL;
 
 	xwayland_view_create(server, xsurface, mapped);
 }
@@ -185,7 +184,12 @@ xwayland_unmanaged_create(struct server *server,
 	struct xwayland_unmanaged *unmanaged = znew(*unmanaged);
 	unmanaged->server = server;
 	unmanaged->xwayland_surface = xsurface;
-	xsurface->data = unmanaged;
+	/*
+	 * xsurface->data is presumed to be a (struct view *) if set,
+	 * so it must be left NULL for an unmanaged surface (it should
+	 * be NULL already at this point).
+	 */
+	assert(!xsurface->data);
 
 	wl_signal_add(&xsurface->events.request_configure,
 		&unmanaged->request_configure);
diff --git a/src/xwayland.c b/src/xwayland.c
index c07a18b7..ec9fe4a2 100644
--- a/src/xwayland.c
+++ b/src/xwayland.c
@@ -221,7 +221,8 @@ handle_destroy(struct wl_listener *listener, void *data)
 	/*
 	 * Break view <-> xsurface association.  Note that the xsurface
 	 * may not actually be destroyed at this point; it may become an
-	 * "unmanaged" surface instead.
+	 * "unmanaged" surface instead (in that case it is important
+	 * that xsurface->data not point to the destroyed view).
 	 */
 	xwayland_view->xwayland_surface->data = NULL;
 	xwayland_view->xwayland_surface = NULL;