diff --git a/doc/fixes36.2 b/doc/fixes36.2
index f499a6351..d7348a2ee 100644
--- a/doc/fixes36.2
+++ b/doc/fixes36.2
@@ -286,6 +286,9 @@ while levitating inside a shop, throwing an unpaid item and having recoil move
 	the shopkeeper and summon kops
 diluted potion of oil is less effective when filling lamps (adds less fuel)
 	or burning (lasts less long) or exploding (inflicts less damage)
+apply fix from grunthack to prevent panic "fakecorr overflow" when vault guard
+	couldn't figure out how to lead the hero from vault to civilization;
+	fixes longstanding bug C343-23
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository
diff --git a/src/vault.c b/src/vault.c
index 0e811d117..c23f55595 100644
--- a/src/vault.c
+++ b/src/vault.c
@@ -1,17 +1,17 @@
-/* NetHack 3.6	vault.c	$NHDT-Date: 1544608469 2018/12/12 09:54:29 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.57 $ */
+/* NetHack 3.6	vault.c	$NHDT-Date: 1545217597 2018/12/19 11:06:37 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.58 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2011. */
 /* NetHack may be freely redistributed.  See license for details. */
 
 #include "hack.h"
 
-STATIC_DCL struct monst *NDECL(findgd);
-
 STATIC_DCL boolean FDECL(clear_fcorr, (struct monst *, BOOLEAN_P));
 STATIC_DCL void FDECL(blackout, (int, int));
 STATIC_DCL void FDECL(restfakecorr, (struct monst *));
 STATIC_DCL void FDECL(parkguard, (struct monst *));
 STATIC_DCL boolean FDECL(in_fcorridor, (struct monst *, int, int));
+STATIC_DCL struct monst *NDECL(findgd);
+STATIC_DCL boolean FDECL(find_guard_dest, (struct monst *, xchar *, xchar *));
 STATIC_DCL void FDECL(move_gold, (struct obj *, int));
 STATIC_DCL void FDECL(wallify_vault, (struct monst *));
 STATIC_DCL void FDECL(gd_mv_monaway, (struct monst *, int, int));
@@ -232,6 +232,44 @@ char *array;
     return '\0';
 }
 
+STATIC_OVL boolean
+find_guard_dest(guard, rx, ry)
+struct monst *guard;
+xchar *rx, *ry;
+{
+    register int x, y, dd, lx = 0, ly = 0;
+
+    for (dd = 2; (dd < ROWNO || dd < COLNO); dd++) {
+        for (y = u.uy - dd; y <= u.uy + dd; ly = y, y++) {
+            if (y < 0 || y > ROWNO - 1)
+                continue;
+            for (x = u.ux - dd; x <= u.ux + dd; lx = x, x++) {
+                if (y != u.uy - dd && y != u.uy + dd && x != u.ux - dd)
+                    x = u.ux + dd;
+                if (x < 1 || x > COLNO - 1)
+                    continue;
+                if (guard && ((x == guard->mx && y == guard->my)
+                              || (guard->isgd && in_fcorridor(guard, x, y))))
+                    continue;
+                if (levl[x][y].typ == CORR) {
+                    lx = (x < u.ux) ? x + 1 : (x > u.ux) ? x - 1 : x;
+                    ly = (y < u.uy) ? y + 1 : (y > u.uy) ? y - 1 : y;
+                    if (levl[lx][ly].typ != STONE && levl[lx][ly].typ != CORR)
+                        goto incr_radius;
+                    *rx = x;
+                    *ry = y;
+                    return TRUE;
+                }
+            }
+        }
+ incr_radius:
+        ;
+    }
+    impossible("Not a single corridor on this level?");
+    tele();
+    return FALSE;
+}
+
 void
 invault()
 {
@@ -252,49 +290,14 @@ invault()
     if (++u.uinvault % VAULT_GUARD_TIME == 0 && !guard) {
         /* if time ok and no guard now. */
         char buf[BUFSZ];
-        register int x, y, dd, gx, gy;
-        int lx = 0, ly = 0;
+        register int x, y, gx, gy;
+        xchar rx, ry;
         long umoney;
 
         /* first find the goal for the guard */
-        for (dd = 2; (dd < ROWNO || dd < COLNO); dd++) {
-            for (y = u.uy - dd; y <= u.uy + dd; ly = y, y++) {
-                if (y < 0 || y > ROWNO - 1)
-                    continue;
-                for (x = u.ux - dd; x <= u.ux + dd; lx = x, x++) {
-                    if (y != u.uy - dd && y != u.uy + dd && x != u.ux - dd)
-                        x = u.ux + dd;
-                    if (x < 1 || x > COLNO - 1)
-                        continue;
-                    if (levl[x][y].typ == CORR) {
-                        if (x < u.ux)
-                            lx = x + 1;
-                        else if (x > u.ux)
-                            lx = x - 1;
-                        else
-                            lx = x;
-                        if (y < u.uy)
-                            ly = y + 1;
-                        else if (y > u.uy)
-                            ly = y - 1;
-                        else
-                            ly = y;
-                        if (levl[lx][ly].typ != STONE
-                            && levl[lx][ly].typ != CORR)
-                            goto incr_radius;
-                        goto fnd;
-                    }
-                }
-            }
-        incr_radius:
-            ;
-        }
-        impossible("Not a single corridor on this level??");
-        tele();
-        return;
-    fnd:
-        gx = x;
-        gy = y;
+        if (!find_guard_dest((struct monst *)0, &rx, &ry))
+            return;
+        gx = rx, gy = ry;
 
         /* next find a good place for a door in the wall */
         x = u.ux;
@@ -621,7 +624,7 @@ gd_move(grd)
 register struct monst *grd;
 {
     int x, y, nx, ny, m, n;
-    int dx, dy, gx, gy, fci;
+    int dx, dy, gx = 0, gy = 0, fci;
     uchar typ;
     struct rm *crm;
     struct fakecorridor *fcp;
@@ -705,7 +708,7 @@ register struct monst *grd;
                 levl[m][n].typ = egrd->fakecorr[0].ftyp;
                 newsym(m, n);
                 grd->mpeaceful = 0;
-            letknow:
+ letknow:
                 if (!cansee(grd->mx, grd->my) || !mon_visible(grd))
                     You_hear("%s.",
                              m_carrying(grd, TIN_WHISTLE)
@@ -848,10 +851,10 @@ register struct monst *grd;
                     goto proceed;
                 }
             }
-        nextnxy:
+ nextnxy:
             ;
         }
-nextpos:
+ nextpos:
     nx = x;
     ny = y;
     gx = egrd->gdx;
@@ -892,19 +895,30 @@ nextpos:
         break;
     }
     crm->typ = CORR;
-proceed:
+ proceed:
     newspot = TRUE;
     unblock_point(nx, ny); /* doesn't block light */
     if (cansee(nx, ny))
         newsym(nx, ny);
 
-    fcp = &(egrd->fakecorr[egrd->fcend]);
-    if (egrd->fcend++ == FCSIZ)
-        panic("fakecorr overflow");
-    fcp->fx = nx;
-    fcp->fy = ny;
-    fcp->ftyp = typ;
-newpos:
+    if ((nx != gx || ny != gy) || (grd->mx != gx || grd->my != gy)) {
+        fcp = &(egrd->fakecorr[egrd->fcend]);
+        if (egrd->fcend++ == FCSIZ)
+            panic("fakecorr overflow");
+        fcp->fx = nx;
+        fcp->fy = ny;
+        fcp->ftyp = typ;
+    } else if (!egrd->gddone) {
+        /* We're stuck, so try to find a new destination. */
+        if (!find_guard_dest(grd, &egrd->gdx, &egrd->gdy)
+            || (egrd->gdx == gx && egrd->gdy == gy)) {
+            pline("%s, confused, disappears.", Monnam(grd));
+            disappear_msg_seen = TRUE;
+            goto cleanup;
+        } else
+            goto nextpos;
+    }
+ newpos:
     gd_mv_monaway(grd, nx, ny);
     if (egrd->gddone) {
         /* The following is a kludge.  We need to keep    */
@@ -916,7 +930,7 @@ newpos:
         /* to avoid a check at the top of this function.  */
         /* At the end of the process, the guard is killed */
         /* in restfakecorr().                             */
-    cleanup:
+ cleanup:
         x = grd->mx, y = grd->my;
         see_guard = canspotmon(grd);
         parkguard(grd); /* move to <0,0> */