--- a/src/sdl/sdlwelldrawing.cxx
+++ b/src/sdl/sdlwelldrawing.cxx
@@ -72,7 +72,7 @@ void SDLWellDrawingEngine::init(int inum_fields, int idx, int idy,
 
 	fields[i]=SDL_DisplayFormat(surface);
 	SDL_FreeSurface(surface);
-	if(fields[i]>0)
+	if(fields[i])
 	    clear_field(i);
     }
     bg_color=colors[BackColor];