--- a/src/sdl/sdl_glimp.c
+++ b/src/sdl/sdl_glimp.c
@@ -372,6 +372,7 @@ static int GLimp_SetMode( qboolean failSafe, qboolean fullscreen, qboolean nobor
 		SDL_GL_SetAttribute( SDL_GL_RED_SIZE, sdlcolorbits );
 		SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, sdlcolorbits );
 		SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, sdlcolorbits );
+		SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 1 );
 		SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, tdepthbits );
 		SDL_GL_SetAttribute( SDL_GL_STENCIL_SIZE, tstencilbits );