diff --git a/polymer/eduke32/source/gamedef.c b/polymer/eduke32/source/gamedef.c
index 370f47180..45fc3ff47 100644
--- a/polymer/eduke32/source/gamedef.c
+++ b/polymer/eduke32/source/gamedef.c
@@ -2232,6 +2232,9 @@ void C_UndefineVolume(int32_t vol)
 {
     Bassert((unsigned)vol < MAXVOLUMES);
 
+    for (int32_t i = 0; i < MAXLEVELS; i++)
+        C_UndefineLevel(vol, i);
+
     EpisodeNames[vol][0] = '\0';
 
     g_numVolumes = 0;
@@ -2270,10 +2273,12 @@ void C_UndefineLevel(int32_t vol, int32_t lev)
     {
         map_t *const map = &MapInfo[(MAXLEVELS*vol)+lev];
 
-        Bfree(map->filename);
+        if (map->filename)
+            Bfree(map->filename);
         map->filename = NULL;
 
-        Bfree(map->name);
+        if (map->name)
+            Bfree(map->name);
         map->name = NULL;
 
         map->partime = 0;
diff --git a/polymer/eduke32/source/gamedef.h b/polymer/eduke32/source/gamedef.h
index 98854f71e..d73c0bb36 100644
--- a/polymer/eduke32/source/gamedef.h
+++ b/polymer/eduke32/source/gamedef.h
@@ -111,17 +111,17 @@ extern vmstate_t vm;
 void G_DoGameStartup(const int32_t *params);
 void C_DefineMusic(int32_t vol, int32_t lev, const char *fn);
 
+void C_UndefineVolume(int32_t vol);
+void C_UndefineSkill(int32_t skill);
+void C_UndefineLevel(int32_t vol, int32_t lev);
 #if defined LUNATIC
 void C_DefineSound(int32_t sndidx, const char *fn, int32_t args[5]);
 void C_DefineQuote(int32_t qnum, const char *qstr);
 void C_DefineVolumeName(int32_t vol, const char *name);
-void C_UndefineVolume(int32_t vol);
 void C_DefineSkillName(int32_t skill, const char *name);
-void C_UndefineSkill(int32_t skill);
 void C_DefineLevelName(int32_t vol, int32_t lev, const char *fn,
                        int32_t partime, int32_t designertime,
                        const char *levelname);
-void C_UndefineLevel(int32_t vol, int32_t lev);
 void C_DefineGameFuncName(int32_t idx, const char *name);
 void C_DefineGameType(int32_t idx, int32_t flags, const char *name);
 int32_t C_SetDefName(const char *name);