diff --git a/js/public/GCAPI.h b/js/public/GCAPI.h
index 9b8c67c9f1ff..407bc68ebdd3 100644
--- a/js/public/GCAPI.h
+++ b/js/public/GCAPI.h
@@ -486,7 +486,7 @@ class JS_PUBLIC_API(AutoCheckCannotGC) : public AutoAssertOnGC
  * JSTRACE_SHAPE. |thing| should be non-null.
  */
 extern JS_FRIEND_API(bool)
-UnmarkGrayGCThingRecursively(void *thing, JSGCTraceKind kind);
+UnmarkGrayGCThingRecursively(GCCellPtr thing);
 
 } /* namespace JS */
 
@@ -509,7 +509,7 @@ ExposeGCThingToActiveJS(JS::GCCellPtr thing)
     if (IsIncrementalBarrierNeededOnTenuredGCThing(rt, thing))
         JS::IncrementalReferenceBarrier(thing);
     else if (JS::GCThingIsMarkedGray(thing.asCell()))
-        JS::UnmarkGrayGCThingRecursively(thing.asCell(), thing.kind());
+        JS::UnmarkGrayGCThingRecursively(thing);
 }
 
 static MOZ_ALWAYS_INLINE void
diff --git a/js/src/gc/Heap.h b/js/src/gc/Heap.h
index d1ef3181b4b2..1c8cc74564c4 100644
--- a/js/src/gc/Heap.h
+++ b/js/src/gc/Heap.h
@@ -196,6 +196,7 @@ class TenuredCell : public Cell
     // Access to the arena header.
     inline ArenaHeader *arenaHeader() const;
     inline AllocKind getAllocKind() const;
+    inline JSGCTraceKind getTraceKind() const;
     inline JS::Zone *zone() const;
     inline JS::Zone *zoneFromAnyThread() const;
     inline bool isInsideZone(JS::Zone *zone) const;
@@ -1312,6 +1313,12 @@ TenuredCell::getAllocKind() const
     return arenaHeader()->getAllocKind();
 }
 
+JSGCTraceKind
+TenuredCell::getTraceKind() const
+{
+    return MapAllocToTraceKind(getAllocKind());
+}
+
 JS::Zone *
 TenuredCell::zone() const
 {
@@ -1346,8 +1353,9 @@ TenuredCell::readBarrier(TenuredCell *thing)
                          MapAllocToTraceKind(thing->getAllocKind()));
         MOZ_ASSERT(tmp == thing);
     }
+    JS::GCCellPtr cellptr(thing, thing->getTraceKind());
     if (JS::GCThingIsMarkedGray(thing))
-        JS::UnmarkGrayGCThingRecursively(thing, MapAllocToTraceKind(thing->getAllocKind()));
+        JS::UnmarkGrayGCThingRecursively(cellptr);
 }
 
 /* static */ MOZ_ALWAYS_INLINE void
diff --git a/js/src/gc/Marking.cpp b/js/src/gc/Marking.cpp
index 3ee8c8e830af..9e6f07e05394 100644
--- a/js/src/gc/Marking.cpp
+++ b/js/src/gc/Marking.cpp
@@ -2110,10 +2110,12 @@ UnmarkGrayChildren(JSTracer *trc, void **thingp, JSGCTraceKind kind)
     tracer->unmarkedAny |= childTracer.unmarkedAny;
 }
 
-JS_FRIEND_API(bool)
-JS::UnmarkGrayGCThingRecursively(void *thing, JSGCTraceKind kind)
+static bool
+UnmarkGrayCellRecursively(gc::Cell *cell, JSGCTraceKind kind)
 {
-    JSRuntime *rt = static_cast<Cell *>(thing)->runtimeFromMainThread();
+    MOZ_ASSERT(cell);
+
+    JSRuntime *rt = cell->runtimeFromMainThread();
 
     // When the ReadBarriered type is used in a HashTable, it is difficult or
     // impossible to suppress the implicit cast operator while iterating for GC.
@@ -2121,16 +2123,28 @@ JS::UnmarkGrayGCThingRecursively(void *thing, JSGCTraceKind kind)
         return false;
 
     bool unmarkedArg = false;
-    if (!IsInsideNursery(static_cast<Cell *>(thing))) {
-        if (!JS::GCThingIsMarkedGray(thing))
+    if (cell->isTenured()) {
+        if (!cell->asTenured().isMarked(GRAY))
             return false;
 
-        TenuredCell::fromPointer(thing)->unmark(js::gc::GRAY);
+        cell->asTenured().unmark(GRAY);
         unmarkedArg = true;
     }
 
     UnmarkGrayTracer trc(rt);
-    JS_TraceChildren(&trc, thing, kind);
+    JS_TraceChildren(&trc, cell, kind);
 
     return unmarkedArg || trc.unmarkedAny;
 }
+
+bool
+js::UnmarkGrayShapeRecursively(Shape *shape)
+{
+    return UnmarkGrayCellRecursively(shape, JSTRACE_SHAPE);
+}
+
+JS_FRIEND_API(bool)
+JS::UnmarkGrayGCThingRecursively(JS::GCCellPtr thing)
+{
+    return UnmarkGrayCellRecursively(thing.asCell(), thing.kind());
+}
diff --git a/js/src/gc/Marking.h b/js/src/gc/Marking.h
index dbd0088cf322..769ae0fa51b6 100644
--- a/js/src/gc/Marking.h
+++ b/js/src/gc/Marking.h
@@ -410,6 +410,9 @@ ToMarkable(Cell *cell)
 void
 TraceChildren(JSTracer *trc, void *thing, JSGCTraceKind kind);
 
+bool
+UnmarkGrayShapeRecursively(Shape *shape);
+
 } /* namespace js */
 
 #endif /* gc_Marking_h */
diff --git a/js/src/jspropertytree.cpp b/js/src/jspropertytree.cpp
index 474274fb556b..bb8187df5783 100644
--- a/js/src/jspropertytree.cpp
+++ b/js/src/jspropertytree.cpp
@@ -172,7 +172,7 @@ PropertyTree::getChild(ExclusiveContext *cx, Shape *parentArg, StackShape &unroo
             parent->removeChild(existingShape);
             existingShape = nullptr;
         } else if (existingShape->isMarked(gc::GRAY)) {
-            JS::UnmarkGrayGCThingRecursively(existingShape, JSTRACE_SHAPE);
+            UnmarkGrayShapeRecursively(existingShape);
         }
     }
 
diff --git a/xpcom/base/CycleCollectedJSRuntime.cpp b/xpcom/base/CycleCollectedJSRuntime.cpp
index b78856f8e86d..cace19f39319 100644
--- a/xpcom/base/CycleCollectedJSRuntime.cpp
+++ b/xpcom/base/CycleCollectedJSRuntime.cpp
@@ -277,7 +277,7 @@ private:
     if (delegateMightNeedMarking && aKey.isObject()) {
       JSObject* kdelegate = js::GetWeakmapKeyDelegate(aKey.toObject());
       if (kdelegate && !xpc_IsGrayGCThing(kdelegate)) {
-        if (JS::UnmarkGrayGCThingRecursively(aKey.asCell(), JSTRACE_OBJECT)) {
+        if (JS::UnmarkGrayGCThingRecursively(aKey)) {
           tracer->mAnyMarked = true;
         }
       }
@@ -287,7 +287,7 @@ private:
         (!aKey || !xpc_IsGrayGCThing(aKey.asCell())) &&
         (!aMap || !xpc_IsGrayGCThing(aMap)) &&
         aValue.kind() != JSTRACE_SHAPE) {
-      if (JS::UnmarkGrayGCThingRecursively(aValue.asCell(), aValue.kind())) {
+      if (JS::UnmarkGrayGCThingRecursively(aValue)) {
         tracer->mAnyMarked = true;
       }
     }