diff --git a/include/decl.h b/include/decl.h
index 6b7142e57..1caf4c5bc 100644
--- a/include/decl.h
+++ b/include/decl.h
@@ -949,6 +949,7 @@ struct instance_globals {
     int mhitu_dieroll;
 
     /* mklev.c */
+    genericptr_t luathemes[MAXDUNGEON];
     xchar vault_x;
     xchar vault_y;
     boolean made_branch; /* used only during level creation */
diff --git a/include/dungeon.h b/include/dungeon.h
index eba96d8bd..b0e3c1b93 100644
--- a/include/dungeon.h
+++ b/include/dungeon.h
@@ -67,7 +67,6 @@ typedef struct dungeon {   /* basic dungeon identifier */
     xchar dunlev_ureached; /* how deep you have been in this dungeon */
     int ledger_start,      /* the starting depth in "real" terms */
         depth_start;       /* the starting depth in "logical" terms */
-    lua_State *themelua;   /* themerms compiled lua */
 } dungeon;
 
 /*
diff --git a/include/extern.h b/include/extern.h
index a5730affc..6d177cb8c 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1325,6 +1325,7 @@ E void NDECL(sort_rooms);
 E void FDECL(add_room, (int, int, int, int, BOOLEAN_P, SCHAR_P, BOOLEAN_P));
 E void FDECL(add_subroom, (struct mkroom *, int, int, int, int, BOOLEAN_P,
                            SCHAR_P, BOOLEAN_P));
+E void FDECL(free_luathemes, (BOOLEAN_P));
 E void NDECL(makecorridors);
 E void FDECL(add_door, (int, int, struct mkroom *));
 E void NDECL(clear_level_structures);
diff --git a/include/patchlevel.h b/include/patchlevel.h
index b02d2d613..24b92cf36 100644
--- a/include/patchlevel.h
+++ b/include/patchlevel.h
@@ -14,7 +14,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 19
+#define EDITLEVEL 20
 
 #define COPYRIGHT_BANNER_A "NetHack, Copyright 1985-2020"
 #define COPYRIGHT_BANNER_B \
diff --git a/src/decl.c b/src/decl.c
index a6de86e35..0f078496b 100644
--- a/src/decl.c
+++ b/src/decl.c
@@ -413,7 +413,7 @@ const struct instance_globals g_init = {
     DUMMY, /* warnsyms */
 
     /* dungeon.c */
-    UNDEFINED_VALUE, /* n_dgns */
+    0, /* n_dgns */
     NULL, /* branches */
     NULL, /* mapseenchn */
 
@@ -478,6 +478,7 @@ const struct instance_globals g_init = {
     UNDEFINED_VALUE, /* mhitu_dieroll */
 
     /* mklev.c */
+    UNDEFINED_VALUES, /* luathemes[] */
     UNDEFINED_VALUE, /* vault_x */
     UNDEFINED_VALUE, /* vault_y */
     UNDEFINED_VALUE, /* made_branch */
diff --git a/src/do.c b/src/do.c
index 530f09a61..8feb069a5 100644
--- a/src/do.c
+++ b/src/do.c
@@ -1420,6 +1420,8 @@ boolean at_stairs, falling, portal;
         update_mlstmv(); /* current monsters are becoming inactive */
         if (nhfp->structlevel)
             bufon(nhfp->fd);       /* use buffered output */
+    } else {
+        free_luathemes(TRUE);
     }
     save_mode = nhfp->mode;
     nhfp->mode = cant_go_back ? FREEING : (WRITING | FREEING);
diff --git a/src/dungeon.c b/src/dungeon.c
index e5c2be68b..f376e5237 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -144,23 +144,24 @@ boolean perform_write, free_data;
             bwrite(nhfp->fd, (genericptr_t) &g.n_dgns, sizeof g.n_dgns);
             bwrite(nhfp->fd, (genericptr_t) g.dungeons,
                    sizeof(dungeon) * (unsigned) g.n_dgns);
-            bwrite(nhfp->fd, (genericptr_t) &g.dungeon_topology, sizeof g.dungeon_topology);
+            bwrite(nhfp->fd, (genericptr_t) &g.dungeon_topology,
+                   sizeof g.dungeon_topology);
             bwrite(nhfp->fd, (genericptr_t) g.tune, sizeof tune);
         }
         for (count = 0, curr = g.branches; curr; curr = curr->next)
             count++;
         if (nhfp->structlevel)
-            bwrite(nhfp->fd, (genericptr_t) &count, sizeof(count));
+            bwrite(nhfp->fd, (genericptr_t) &count, sizeof count);
 
         for (curr = g.branches; curr; curr = curr->next) {
           if (nhfp->structlevel)
-              bwrite(nhfp->fd, (genericptr_t) curr, sizeof(branch));
+              bwrite(nhfp->fd, (genericptr_t) curr, sizeof *curr);
         }
         count = maxledgerno();
         if (nhfp->structlevel) { 
             bwrite(nhfp->fd, (genericptr_t) &count, sizeof count);
             bwrite(nhfp->fd, (genericptr_t) g.level_info,
-                   (unsigned) count * sizeof(struct linfo));
+                   (unsigned) count * sizeof (struct linfo));
             bwrite(nhfp->fd, (genericptr_t) &g.inv_pos, sizeof g.inv_pos);
         }
         for (count = 0, curr_ms = g.mapseenchn; curr_ms;
@@ -168,7 +169,7 @@ boolean perform_write, free_data;
             count++;
 
         if (nhfp->structlevel)
-            bwrite(nhfp->fd, (genericptr_t) &count, sizeof(count));
+            bwrite(nhfp->fd, (genericptr_t) &count, sizeof count);
 
         for (curr_ms = g.mapseenchn; curr_ms; curr_ms = curr_ms->next) {
             save_mapseen(nhfp, curr_ms);
@@ -203,23 +204,22 @@ NHFILE *nhfp;
     mapseen *curr_ms, *last_ms;
 
     if (nhfp->structlevel) {
-        mread(nhfp->fd, (genericptr_t) &g.n_dgns, sizeof(g.n_dgns));
-        mread(nhfp->fd, (genericptr_t) g.dungeons, sizeof(dungeon) * (unsigned) g.n_dgns);
-        mread(nhfp->fd, (genericptr_t) &g.dungeon_topology, sizeof g.dungeon_topology);
+        mread(nhfp->fd, (genericptr_t) &g.n_dgns, sizeof g.n_dgns);
+        mread(nhfp->fd, (genericptr_t) g.dungeons,
+              sizeof (dungeon) * (unsigned) g.n_dgns);
+        mread(nhfp->fd, (genericptr_t) &g.dungeon_topology,
+              sizeof g.dungeon_topology);
         mread(nhfp->fd, (genericptr_t) g.tune, sizeof tune);
     }
     last = g.branches = (branch *) 0;
 
-    for (i = 0; i < g.n_dgns; i++)
-        g.dungeons[i].themelua = (lua_State *) 0;
-
     if (nhfp->structlevel)
-        mread(nhfp->fd, (genericptr_t) &count, sizeof(count));
+        mread(nhfp->fd, (genericptr_t) &count, sizeof count);
 
     for (i = 0; i < count; i++) {
-        curr = (branch *) alloc(sizeof(branch));
+        curr = (branch *) alloc(sizeof *curr);
         if (nhfp->structlevel)
-            mread(nhfp->fd, (genericptr_t) curr, sizeof(branch));
+            mread(nhfp->fd, (genericptr_t) curr, sizeof *curr);
         curr->next = (branch *) 0;
         if (last)
             last->next = curr;
@@ -229,18 +229,18 @@ NHFILE *nhfp;
     }
 
     if (nhfp->structlevel)
-        mread(nhfp->fd, (genericptr_t) &count, sizeof(count));
+        mread(nhfp->fd, (genericptr_t) &count, sizeof count);
 
     if (count >= MAXLINFO)
         panic("level information count larger (%d) than allocated size",
               count);
     if (nhfp->structlevel)
         mread(nhfp->fd, (genericptr_t) g.level_info,
-              (unsigned) count * sizeof(struct linfo));
+              (unsigned) count * sizeof (struct linfo));
 
     if (nhfp->structlevel) {
         mread(nhfp->fd, (genericptr_t) &g.inv_pos, sizeof g.inv_pos);
-        mread(nhfp->fd, (genericptr_t) &count, sizeof(count));
+        mread(nhfp->fd, (genericptr_t) &count, sizeof count);
     }
 
     last_ms = (mapseen *) 0;
@@ -1030,7 +1030,6 @@ init_dungeons()
         Strcpy(g.dungeons[i].dname, dgn_name); /* FIXME: dname length */
         Strcpy(g.dungeons[i].proto, dgn_protoname); /* FIXME: proto length */
         Strcpy(g.dungeons[i].themerms, dgn_themerms); /* FIXME: length */
-        g.dungeons[i].themelua = (lua_State *) 0;
         g.dungeons[i].boneid = *dgn_bonetag ? *dgn_bonetag : 0;
         free((genericptr) dgn_fill);
         /* free((genericptr) dgn_protoname); -- stored in pd.tmpdungeon[] */
diff --git a/src/mklev.c b/src/mklev.c
index 71f6f4bef..007262ea0 100644
--- a/src/mklev.c
+++ b/src/mklev.c
@@ -239,30 +239,46 @@ boolean special;
     g.nsubroom++;
 }
 
+void
+free_luathemes(keependgame)
+boolean keependgame; /* False: exiting, True: discarding main dungeon */
+{
+    int i;
+
+    for (i = 0; i < g.n_dgns; ++i) {
+        if (keependgame && i == astral_level.dnum)
+            continue;
+        if (g.luathemes[i]) {
+            lua_close((lua_State *) g.luathemes[i]);
+            g.luathemes[i] = (lua_State *) 0;
+        }
+    }
+}
+
 static void
 makerooms()
 {
     boolean tried_vault = FALSE;
     int themeroom_tries = 0;
-    boolean dothemes = (g.dungeons[u.uz.dnum].themelua != NULL);
-    char *fname = g.dungeons[u.uz.dnum].themerms;
+    char *fname;
+    lua_State *themes = (lua_State *) g.luathemes[u.uz.dnum];
 
-    if (*fname && !g.dungeons[u.uz.dnum].themelua) {
-        g.dungeons[u.uz.dnum].themelua = nhl_init();
-        if (g.dungeons[u.uz.dnum].themelua) {
-            if (!nhl_loadlua(g.dungeons[u.uz.dnum].themelua, fname)) {
+    if (!themes && *(fname = g.dungeons[u.uz.dnum].themerms)) {
+        if ((themes = nhl_init()) != 0) {
+            if (!nhl_loadlua(themes, fname)) {
                 /* loading lua failed, don't use themed rooms */
-                g.dungeons[u.uz.dnum].themerms[0] = '\0';
-                lua_close(g.dungeons[u.uz.dnum].themelua);
-                g.dungeons[u.uz.dnum].themelua = NULL;
-                dothemes = FALSE;
+                lua_close(themes);
+                themes = (lua_State *) 0;
             } else {
-                dothemes = TRUE;
+                /* success; save state for this dungeon branch */
+                g.luathemes[u.uz.dnum] = (genericptr_t) themes;
             }
         }
+        if (!themes) /* don't try again when making next level */
+            *fname = '\0'; /* g.dungeons[u.uz.dnum].themerms */
     }
 
-    if (dothemes) {
+    if (themes) {
         create_des_coder();
     }
 
@@ -277,12 +293,11 @@ makerooms()
                 g.rooms[g.nroom].hx = -1;
             }
         } else {
-            if (dothemes) {
+            if (themes) {
                 g.in_mk_themerooms = TRUE;
                 g.themeroom_failed = FALSE;
-                lua_getglobal(g.dungeons[u.uz.dnum].themelua,
-                              "themerooms_generate");
-                lua_call(g.dungeons[u.uz.dnum].themelua, 0, 0);
+                lua_getglobal(themes, "themerooms_generate");
+                lua_call(themes, 0, 0);
                 g.in_mk_themerooms = FALSE;
                 if (g.themeroom_failed
                     && ((themeroom_tries++ > 10)
@@ -294,7 +309,7 @@ makerooms()
             }
         }
     }
-    if (dothemes) {
+    if (themes) {
         wallification(1, 0, COLNO - 1, ROWNO - 1);
         free(g.coder);
         g.coder = NULL;
diff --git a/src/save.c b/src/save.c
index c2d710f4c..b3fe86656 100644
--- a/src/save.c
+++ b/src/save.c
@@ -1070,17 +1070,12 @@ free_dungeons()
 {
 #ifdef FREE_ALL_MEMORY
     NHFILE tnhfp;
-    int i;
 
     zero_nhfile(&tnhfp);    /* also sets fd to -1 */
     tnhfp.mode = FREEING;
     savelevchn(&tnhfp);
     save_dungeon(&tnhfp, FALSE, TRUE);
-    for (i = 0; i < g.n_dgns; i++)
-        if (g.dungeons[i].themelua) {
-            lua_close(g.dungeons[i].themelua);
-            g.dungeons[i].themelua = (lua_State *) 0;
-        }
+    free_luathemes(TRUE);
 #endif
     return;
 }