diff --git a/src/sdl/i_main.c b/src/sdl/i_main.c
index 32cc16208a3e15b3d79d7110eee8faad79f4b358..326f1a9291ab10407817dd2df54cf0bc22c5dcca 100644
--- a/src/sdl/i_main.c
+++ b/src/sdl/i_main.c
@@ -143,7 +143,7 @@ int main(int argc, char **argv)
 		if (M_CheckParm("-logfile") && M_IsNextParm())
 			format = M_GetNextParm();
 		else
-			format = "log-%Y-%m-%d %H-%M-%S.txt";
+			format = "log-%Y-%m-%d_%H-%M-%S.txt";
 
 		strftime(logfile, sizeof logfile, format, timeinfo);