diff --git a/backends/sdl/sdl-common.cpp b/backends/sdl/sdl-common.cpp
index af809591fc2..6578cf7685f 100644
--- a/backends/sdl/sdl-common.cpp
+++ b/backends/sdl/sdl-common.cpp
@@ -59,6 +59,7 @@ void OSystem_SDL_Common::init_intern(int gfx_mode, bool full_screen, bool aspect
 	_mode = gfx_mode;
 	_full_screen = full_screen;
 	_adjustAspectRatio = aspect_ratio;
+	_mode_flags = 0;
 
 	if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER | SDL_INIT_JOYSTICK) ==-1) {
 		error("Could not initialize SDL: %s.\n", SDL_GetError());
diff --git a/backends/sdl/sdl.cpp b/backends/sdl/sdl.cpp
index 8d73295be4e..b95d7a27755 100644
--- a/backends/sdl/sdl.cpp
+++ b/backends/sdl/sdl.cpp
@@ -56,7 +56,7 @@ OSystem_SDL::OSystem_SDL()
 
 void OSystem_SDL::load_gfx_mode() {
 	_forceFull = true;
-	_mode_flags = DF_UPDATE_EXPAND_1_PIXEL;
+	_mode_flags |= DF_UPDATE_EXPAND_1_PIXEL;
 
 	_tmpscreen = NULL;
 	_tmpScreenWidth = (_screenWidth + 3);
diff --git a/backends/sdl/sdl_gl.cpp b/backends/sdl/sdl_gl.cpp
index e58ce505e1f..cc307eae58a 100644
--- a/backends/sdl/sdl_gl.cpp
+++ b/backends/sdl/sdl_gl.cpp
@@ -94,7 +94,7 @@ void OSystem_SDL_OpenGL::load_gfx_mode() {
 	Amask = 0;
 
 	_forceFull = true;
-	_mode_flags = DF_UPDATE_EXPAND_1_PIXEL;
+	_mode_flags |= DF_UPDATE_EXPAND_1_PIXEL;
 
 	_tmpscreen = NULL;
 	_tmpScreenWidth = (_screenWidth + 3);