diff --git a/imgui.cpp b/imgui.cpp
index f1c3af41..04105d52 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -4517,7 +4517,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->Size = window->Collapsed ? window->TitleBarRect().GetSize() : window->SizeFull;
         if ((flags & ImGuiWindowFlags_ChildWindow) && !(flags & ImGuiWindowFlags_Popup))
         {
-            IM_ASSERT(window_size_x_set_by_api && window_size_x_set_by_api); // Submitted by BeginChild()
+            IM_ASSERT(window_size_x_set_by_api && window_size_y_set_by_api); // Submitted by BeginChild()
             window->Size = window->SizeFull;
         }