diff --git a/backends/imgui_impl_sdl3.cpp b/backends/imgui_impl_sdl3.cpp
index 5b0c82d9..4427f2c8 100644
--- a/backends/imgui_impl_sdl3.cpp
+++ b/backends/imgui_impl_sdl3.cpp
@@ -19,6 +19,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2023-05-04: Fixed build on Emscripten/iOS/Android. (#6391)
 //  2023-04-06: Inputs: Avoid calling SDL_StartTextInput()/SDL_StopTextInput() as they don't only pertain to IME. It's unclear exactly what their relation is to IME. (#6306)
 //  2023-04-04: Inputs: Added support for io.AddMouseSourceEvent() to discriminate ImGuiMouseSource_Mouse/ImGuiMouseSource_TouchScreen. (#2702)
 //  2023-02-23: Accept SDL_GetPerformanceCounter() not returning a monotonically increasing value. (#6189, #6114, #3644)
@@ -441,6 +442,7 @@ static void ImGui_ImplSDL3_UpdateMouseData()
     SDL_Window* focused_window = SDL_GetKeyboardFocus();
     const bool is_app_focused = (bd->Window == focused_window);
 #else
+    SDL_Window* focused_window = bd->Window;
     const bool is_app_focused = (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_INPUT_FOCUS) != 0; // SDL 2.0.3 and non-windowed systems: single-viewport only
 #endif
     if (is_app_focused)
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 3411485d..ba15f843 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -63,6 +63,7 @@ Other changes:
   Win32/Winapi with OpenGL. (#3218)
 - Backends: OpenGL3: Restore front and back polygon mode separately when supported
   by context (Desktop 3.0, 3.1, or 3.2+ with compat bit). (#6333) [@GereonV]
+- Backends: SDL3: Fixed build on Emscripten/iOS/Android. (#6391) [@jo-codegirl]
 - Examples: Added native Win32+OpenGL3 example. We don't recommend using this setup but we
   provide it for completeness. (#3218, #5170, #6086, #2772, #2600, #2359, #2022, #1553) [@learn-more]
 - Examples: Vulkan: Use integrated GPU if nothing else is available. (#6359) [@kimidaisuki22]