diff --git a/src/mon.c b/src/mon.c
index f04e2418c..6ad8a0fb5 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -3433,6 +3433,8 @@ set_ustuck(struct monst *mtmp)
 
     disp.botl = TRUE;
     u.ustuck = mtmp;
+    if (u.ustuck_mid)
+        u.ustuck_mid = 0;
     if (!u.ustuck) {
         u.uswallow = 0;
         u.uswldtim = 0;
diff --git a/src/restore.c b/src/restore.c
index 5ab2342c7..8a7ad8743 100644
--- a/src/restore.c
+++ b/src/restore.c
@@ -1219,8 +1219,7 @@ getlev(NHFILE *nhfp, int pid, xint8 lev)
             u.usteed_mid = 0;
         } else {
             if (mtmp->m_id == u.ustuck_mid) {
-                set_ustuck(mtmp);
-                u.ustuck_mid = 0;
+                set_ustuck(mtmp); /* set_ustuck clears u.ustuck_mid */
             }
             place_monster(mtmp, mtmp->mx, mtmp->my);
             if (mtmp->wormno)
diff --git a/src/save.c b/src/save.c
index d03000408..7eb7f5eb6 100644
--- a/src/save.c
+++ b/src/save.c
@@ -285,13 +285,32 @@ savegamestate(NHFILE *nhfp)
     Sfo_long(nhfp, &svw.wreserve, "wreserve");
     Sfo_int32(nhfp, &svw.wtreserved, "wtreserved");
     /*
-     * It is critical to ensure that u.ustuck_mid and u.usteed_mid
-     * hold current and correct data, in case this is needed by
-     * recover.
+     * In a normal save operation initiated by the player,
+     * the u.ustuck_mid and u.usteed_mid were already set
+     * by savemonchn() called from savelev_core(). Under
+     * that operation, u.ustuck and u.usteed pointers no longer
+     * point to valid locations here. Their non-zero values serve
+     * only to flag that they are were set, but the pointers
+     * must not be dereferenced.
      */
-    u.ustuck_mid = (u.ustuck) ? u.ustuck->m_id : 0;
-    u.usteed_mid = (u.usteed) ? u.usteed->m_id : 0;
+    if (program_state.in_checkpoint) {
+        /*
+         * It is critical to ensure that u.ustuck_mid and u.usteed_mid
+         * hold current and correct data, in case this is needed by
+         * recover. The pointers, if set, are still pointing at
+         * valid data during a checkpoint operation, unlike during
+         * a synchronized save operation.
+         */
+        u.ustuck_mid = (u.ustuck) ? u.ustuck->m_id : 0;
+        u.usteed_mid = (u.usteed) ? u.usteed->m_id : 0;
+    }
     Sfo_you(nhfp, &u, "gamestate-you");
+
+    /* clear the in-memory value of these, now that they have been
+     * successfully written out.
+     */
+    u.ustuck_mid = 0;
+    u.usteed_mid = 0;
     Sfo_char(nhfp, yyyymmddhhmmss(ubirthday), "gamestate-ubirthday", 14);
     Sfo_long(nhfp, &urealtime.realtime, "gamestate-realtime");
     Sfo_char(nhfp, yyyymmddhhmmss(urealtime.start_timing), "gamestate-start_timing", 14);