diff --git a/apps/plugins/doom/d_deh.h b/apps/plugins/doom/d_deh.h
index 0844c38be1..0d65260b18 100644
--- a/apps/plugins/doom/d_deh.h
+++ b/apps/plugins/doom/d_deh.h
@@ -86,7 +86,7 @@ extern const char *s_QLPROMPT; // = QLPROMPT;
 "you can't start a new game\n"\
 "while in a network game.\n\n"PRESSKEY
 */
-extern char *s_NEWGAME; // = NEWGAME;
+extern const char *s_NEWGAME; // = NEWGAME;
 
 // CPhipps - message given when asked if to restart the level
 extern char *s_RESTARTLEVEL;
diff --git a/apps/plugins/doom/g_game.c b/apps/plugins/doom/g_game.c
index d4445254f0..f970b66b5a 100644
--- a/apps/plugins/doom/g_game.c
+++ b/apps/plugins/doom/g_game.c
@@ -844,7 +844,7 @@ void G_Ticker (void)
             if ((netgame || demoplayback) && cmd->forwardmove > TURBOTHRESHOLD &&
                   !(gametic&31) && ((gametic>>5)&3) == i )
             {
-               extern char *player_names[];
+               extern const char *player_names[];
                /* cph - don't use sprintf, use doom_printf */
                doom_printf ("%s is turbo!", player_names[i]);
             }
@@ -2241,7 +2241,7 @@ void G_RecordDemo (const char* name)
 // byte(s) should still be skipped over or padded with 0's.
 // Lee Killough 3/1/98
 
-extern int forceOldBsp;
+extern boolean forceOldBsp;
 
 byte *G_WriteOptions(byte *demo_p)
 {
diff --git a/apps/plugins/doom/hu_stuff.c b/apps/plugins/doom/hu_stuff.c
index 5361435fd5..639c963f72 100644
--- a/apps/plugins/doom/hu_stuff.c
+++ b/apps/plugins/doom/hu_stuff.c
@@ -227,18 +227,6 @@ extern int armor_red;
 extern int armor_yellow;
 extern int armor_green;
 
-//
-// Builtin map names.
-// The actual names can be found in DStrings.h.
-//
-// Ty 03/27/98 - externalized map name arrays - now in d_deh.c
-// and converted to arrays of pointers to char *
-// See modified HUTITLEx macros
-extern char **mapnames[];
-extern char **mapnames2[];
-extern char **mapnamesp[];
-extern char **mapnamest[];
-
 // key tables
 // jff 5/10/98 french support removed,
 // as it was not being used and couldn't be easily tested
diff --git a/apps/plugins/doom/hu_stuff.h b/apps/plugins/doom/hu_stuff.h
index c0e927d4bb..8946e06220 100644
--- a/apps/plugins/doom/hu_stuff.h
+++ b/apps/plugins/doom/hu_stuff.h
@@ -84,9 +84,9 @@ extern int hud_displayed;   /* hud is displayed */
 extern int hud_active;      /* hud mode 0=off, 1=small, 2=full          */
 extern int hud_nosecrets;   /* status does not list secrets/items/kills */
 
-extern char **mapnames[];
-extern char **mapnames2[];
-extern char **mapnamesp[];
-extern char **mapnamest[];
+extern const char ** const mapnames[];
+extern const char ** const mapnames2[];
+extern const char ** const mapnamesp[];
+extern const char ** const mapnamest[];
 
 #endif