diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index cf6e555f0..463203200 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -85,6 +85,8 @@ Other Changes:
 
 Docking+Viewports Branch:
 
+- Fixed an assert in background dimming code, which could trigger after using
+  gamepad/keyboard to move a window to another viewport. (#9053) [@lut0pia, @ocornut]
 - Backends:
   - Win32: viewports created by backend forcefully direct messages to
     DefWindowProcW() in order to support Unicode text input. (#9099, #3653, #5961) [@ulhc]
diff --git a/imgui.cpp b/imgui.cpp
index 272881c75..55af463c3 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -6025,15 +6025,16 @@ static void ImGui::RenderDimmedBackgroundBehindWindow(ImGuiWindow* window, ImU32
     // Draw behind window by moving the draw command at the FRONT of the draw list
     {
         // Draw list have been trimmed already, hence the explicit recreation of a draw command if missing.
-        // FIXME: This is creating complication, might be simpler if we could inject a drawlist in drawdata at a given position and not attempt to manipulate ImDrawCmd order.
+        // FIXME: This is a little bit complicated, solely to avoid creating/injecting an extra drawlist in drawdata.
         ImDrawList* draw_list = window->RootWindowDockTree->DrawList;
         draw_list->ChannelsMerge();
         if (draw_list->CmdBuffer.Size == 0)
             draw_list->AddDrawCmd();
         draw_list->PushClipRect(viewport_rect.Min - ImVec2(1, 1), viewport_rect.Max + ImVec2(1, 1), false); // FIXME: Need to stricty ensure ImDrawCmd are not merged (ElemCount==6 checks below will verify that)
-        draw_list->AddRectFilled(viewport_rect.Min, viewport_rect.Max, col);
         ImDrawCmd cmd = draw_list->CmdBuffer.back();
-        IM_ASSERT(cmd.ElemCount == 6);
+        IM_ASSERT(cmd.ElemCount == 0);
+        draw_list->AddRectFilled(viewport_rect.Min, viewport_rect.Max, col);
+        cmd = draw_list->CmdBuffer.back();
         draw_list->CmdBuffer.pop_back();
         draw_list->CmdBuffer.push_front(cmd);
         draw_list->AddDrawCmd(); // We need to create a command as CmdBuffer.back().IdxOffset won't be correct if we append to same command.
@@ -6095,10 +6096,12 @@ static void ImGui::RenderDimmedBackgrounds()
     {
         // Draw dimming behind Ctrl+Tab target window and behind Ctrl+Tab UI window
         RenderDimmedBackgroundBehindWindow(g.NavWindowingTargetAnim, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
-        if (g.NavWindowingListWindow != NULL && g.NavWindowingListWindow->Viewport && g.NavWindowingListWindow->Viewport != g.NavWindowingTargetAnim->Viewport)
-            RenderDimmedBackgroundBehindWindow(g.NavWindowingListWindow, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
         viewports_already_dimmed[0] = g.NavWindowingTargetAnim->Viewport;
-        viewports_already_dimmed[1] = g.NavWindowingListWindow ? g.NavWindowingListWindow->Viewport : NULL;
+        if (g.NavWindowingListWindow != NULL && g.NavWindowingListWindow->Active && g.NavWindowingListWindow->Viewport && g.NavWindowingListWindow->Viewport != g.NavWindowingTargetAnim->Viewport)
+        {
+            RenderDimmedBackgroundBehindWindow(g.NavWindowingListWindow, GetColorU32(ImGuiCol_NavWindowingDimBg, g.DimBgRatio));
+            viewports_already_dimmed[1] = g.NavWindowingListWindow->Viewport;
+        }
 
         // Draw border around Ctrl+Tab target window
         ImGuiWindow* window = g.NavWindowingTargetAnim;