diff --git a/doc/fixes36.2 b/doc/fixes36.2
index b080b417d..e9484a622 100644
--- a/doc/fixes36.2
+++ b/doc/fixes36.2
@@ -295,6 +295,8 @@ if hero kicks some embedded gold out of a wall while following vault gaurd
 	the gold" unless he's on brink of going ballistic
 for '/?' information lookup, "item named The Artifact" failed to find info
 	about "Artifact" due to presence of "The"
+identifying or forgetting gem types now adjusts prices for gems already on
+	shopping bill
 
 
 Fixes to Post-3.6.1 Problems that Were Exposed Via git Repository
diff --git a/include/extern.h b/include/extern.h
index bd0255c2a..78c7647da 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1,4 +1,4 @@
-/* NetHack 3.6	extern.h	$NHDT-Date: 1545182146 2018/12/19 01:15:46 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.674 $ */
+/* NetHack 3.6	extern.h	$NHDT-Date: 1545383614 2018/12/21 09:13:34 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.675 $ */
 /* Copyright (c) Steve Creps, 1988.				  */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -2220,6 +2220,7 @@ E long FDECL(contained_cost,
              (struct obj *, struct monst *, long, BOOLEAN_P, BOOLEAN_P));
 E long FDECL(contained_gold, (struct obj *));
 E void FDECL(picked_container, (struct obj *));
+E void FDECL(gem_learned, (int));
 E void FDECL(alter_cost, (struct obj *, long));
 E long FDECL(unpaid_cost, (struct obj *, BOOLEAN_P));
 E boolean FDECL(billable, (struct monst **, struct obj *, CHAR_P, BOOLEAN_P));
diff --git a/src/o_init.c b/src/o_init.c
index b4fc440ee..b2d28f50e 100644
--- a/src/o_init.c
+++ b/src/o_init.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	o_init.c	$NHDT-Date: 1528332336 2018/06/07 00:45:36 $  $NHDT-Branch: NetHack-3.6.2 $:$NHDT-Revision: 1.24 $ */
+/* NetHack 3.6	o_init.c	$NHDT-Date: 1545383615 2018/12/21 09:13:35 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.25 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2011. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -362,8 +362,11 @@ boolean credit_hero;
                 exercise(A_WIS, TRUE);
         }
         /* moves==1L => initial inventory, gameover => final disclosure */
-        if (moves > 1L && !program_state.gameover)
+        if (moves > 1L && !program_state.gameover) {
+            if (objects[oindx].oc_class == GEM_CLASS)
+                gem_learned(oindx); /* could affect price of unpaid gems */
             update_inventory();
+        }
     }
 }
 
@@ -390,6 +393,9 @@ register int oindx;
             disco[dindx - 1] = 0;
         else
             impossible("named object not in disco");
+
+        if (objects[oindx].oc_class == GEM_CLASS)
+            gem_learned(oindx); /* ok, it's actually been unlearned */
         update_inventory();
     }
 }
diff --git a/src/shk.c b/src/shk.c
index 1a50616e9..315de4c1d 100644
--- a/src/shk.c
+++ b/src/shk.c
@@ -1,4 +1,4 @@
-/* NetHack 3.6	shk.c	$NHDT-Date: 1545036290 2018/12/17 08:44:50 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.143 $ */
+/* NetHack 3.6	shk.c	$NHDT-Date: 1545383616 2018/12/21 09:13:36 $  $NHDT-Branch: NetHack-3.6.2-beta01 $:$NHDT-Revision: 1.144 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -2278,6 +2278,45 @@ register struct monst *shkp;
     return tmp;
 }
 
+/* unlike alter_cost() which operates on a specific item, identifying or
+   forgetting a gem causes all unpaid gems of its type to change value */
+void
+gem_learned(oindx)
+int oindx;
+{
+    struct obj *obj;
+    struct monst *shkp;
+    struct bill_x *bp;
+    int ct;
+
+    /*
+     * Unfortunately, shop bill doesn't have object type included,
+     * just obj->oid for each unpaid stack, so we have to go through
+     * every bill and every item on that bill and match up against
+     * every unpaid stack on the level....
+     *
+     * Fortunately, there's no need to catch up when changing dungeon
+     * levels even if we ID'd or forget some gems while gone from a
+     * level.  There won't be any shop bills when arriving; they were
+     * either paid before leaving or got treated as robbery and it's
+     * too late to adjust pricing.
+     */
+    for (shkp = next_shkp(fmon, TRUE); shkp;
+         shkp = next_shkp(shkp->nmon, TRUE)) {
+        ct = ESHK(shkp)->billct;
+        bp = ESHK(shkp)->bill;
+        while (--ct >= 0) {
+            obj = find_oid(bp->bo_id);
+            if (!obj) /* shouldn't happen */
+                continue;
+            if ((oindx != STRANGE_OBJECT) ? (obj->otyp == oindx)
+                                          : (obj->oclass == GEM_CLASS))
+                bp->price = get_cost(obj, shkp);
+            ++bp;
+        }
+    }
+}
+
 /* called when an item's value has been enhanced; if it happens to be
    on any shop bill, update that bill to reflect the new higher price
    [if the new price drops for some reason, keep the old one in place] */