diff --git a/src/window.c b/src/window.c
index 70eb3283..5e74e6e0 100644
--- a/src/window.c
+++ b/src/window.c
@@ -628,6 +628,8 @@ GLFWAPI void glfwRestoreWindow(GLFWwindow* handle)
 GLFWAPI void glfwMaximizeWindow(GLFWwindow* handle)
 {
     _GLFWwindow* window = (_GLFWwindow*) handle;
+    assert(window != NULL);
+
     _GLFW_REQUIRE_INIT();
     _glfwPlatformMaximizeWindow(window);
 }