diff --git a/xwayland/window-manager.c b/xwayland/window-manager.c
index 70c8cf7..d475e36 100644
--- a/xwayland/window-manager.c
+++ b/xwayland/window-manager.c
@@ -2218,8 +2218,8 @@
 		parent = window->transient_for;
 		shell_interface->set_transient(window->shsurf,
 					       parent->surface,
-					       parent->x - window->x,
-					       parent->y - window->y, 0);
+					       window->x - parent->x,
+					       window->y - parent->y, 0);
 	} else {
 		shell_interface->set_toplevel(window->shsurf);
 	}