diff --git a/Quake/gl_vidnt.c b/Quake/gl_vidnt.c
index 63bcbc32..e1fc2b82 100644
--- a/Quake/gl_vidnt.c
+++ b/Quake/gl_vidnt.c
@@ -2179,6 +2179,8 @@ void	VID_Init (void)
 
 				if (COM_CheckParm("-height"))
 					height = Q_atoi(com_argv[COM_CheckParm("-height")+1]);
+				else
+					height = width * 3 / 4; // assume 4:3 aspect ratio
 
 			// if they want to force it, add the specified mode to the list
 				if (COM_CheckParm("-force") && (nummodes < MAX_MODE_LIST))
diff --git a/Quake/gl_vidsdl.c b/Quake/gl_vidsdl.c
index cdb59425..9c932be0 100644
--- a/Quake/gl_vidsdl.c
+++ b/Quake/gl_vidsdl.c
@@ -1262,6 +1262,8 @@ void	VID_Init (void)
 
 				if (COM_CheckParm("-height"))
 					height = Q_atoi(com_argv[COM_CheckParm("-height")+1]);
+				else
+					height = width * 3 / 4; // assume 4:3 aspect ratio
 
 			// if they want to force it, add the specified mode to the list
 				if (COM_CheckParm("-force") && (nummodes < MAX_MODE_LIST))