diff --git a/kitty/glfw.c b/kitty/glfw.c
index 4953f9e21..3ff8ce5ee 100644
--- a/kitty/glfw.c
+++ b/kitty/glfw.c
@@ -840,7 +840,7 @@ static PyObject*
 glfw_get_key_name(PyObject UNUSED *self, PyObject *args) {
     int key, native_key;
     if (!PyArg_ParseTuple(args, "ii", &key, &native_key)) return NULL;
-    return Py_BuildValue("s", glfwGetKeyName(key, native_key));
+    return Py_BuildValue("z", glfwGetKeyName(key, native_key));
 }
 
 static PyObject*