diff --git a/js/src/vm/NativeObject.cpp b/js/src/vm/NativeObject.cpp
index bbf50eaab7445..ba53d0566288d 100644
--- a/js/src/vm/NativeObject.cpp
+++ b/js/src/vm/NativeObject.cpp
@@ -498,7 +498,7 @@ NativeObject::sparsifyDenseElement(JSContext* cx, HandleNativeObject obj, uint32
     // extensibility check if we're, for example, sparsifying frozen objects..
     if (!addDataPropertyInternal(cx, obj, id, slot,
                                  obj->getElementsHeader()->elementAttributes(),
-                                 0, entry, true, keep)) {
+                                 entry, keep)) {
         obj->setDenseElementUnchecked(index, value);
         return false;
     }
@@ -1151,22 +1151,13 @@ NativeObject::freeSlot(JSContext* cx, uint32_t slot)
     setSlot(slot, UndefinedValue());
 }
 
-/* static */ Shape*
-NativeObject::addDataProperty(JSContext* cx, HandleNativeObject obj,
-                              jsid idArg, uint32_t slot, unsigned attrs)
-{
-    MOZ_ASSERT(!(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
-    RootedId id(cx, idArg);
-    return addDataProperty(cx, obj, id, slot, attrs, 0);
-}
-
 /* static */ Shape*
 NativeObject::addDataProperty(JSContext* cx, HandleNativeObject obj,
                               HandlePropertyName name, uint32_t slot, unsigned attrs)
 {
     MOZ_ASSERT(!(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
     RootedId id(cx, NameToId(name));
-    return addDataProperty(cx, obj, id, slot, attrs, 0);
+    return addDataProperty(cx, obj, id, slot, attrs);
 }
 
 template <AllowGC allowGC>
@@ -1432,7 +1423,7 @@ AddOrChangeProperty(JSContext* cx, HandleNativeObject obj, HandleId id,
     if (AddOrChange == IsAddOrChange::Add) {
         if (Shape::isDataProperty(desc.attributes(), desc.getter(), desc.setter())) {
             shape = NativeObject::addDataProperty(cx, obj, id, SHAPE_INVALID_SLOT,
-                                                  desc.attributes(), 0);
+                                                  desc.attributes());
         } else {
             shape = NativeObject::addAccessorProperty(cx, obj, id, desc.getter(), desc.setter(),
                                                       desc.attributes(), 0);
diff --git a/js/src/vm/NativeObject.h b/js/src/vm/NativeObject.h
index 3fd671abb9b10..f8ce2cec3c342 100644
--- a/js/src/vm/NativeObject.h
+++ b/js/src/vm/NativeObject.h
@@ -854,8 +854,8 @@ class NativeObject : public ShapedObject
   public:
     /* Add a property whose id is not yet in this scope. */
     static MOZ_ALWAYS_INLINE Shape* addDataProperty(JSContext* cx, HandleNativeObject obj, HandleId id,
-                                                    uint32_t slot, unsigned attrs, unsigned flags,
-                                                    bool allowDictionary = true);
+                                                    uint32_t slot, unsigned attrs);
+
     static MOZ_ALWAYS_INLINE Shape* addAccessorProperty(JSContext* cx, HandleNativeObject obj, HandleId id,
                                                         JSGetterOp getter, JSSetterOp setter,
                                                         unsigned attrs, unsigned flags,
@@ -863,8 +863,6 @@ class NativeObject : public ShapedObject
     static Shape* addEnumerableDataProperty(JSContext* cx, HandleNativeObject obj, HandleId id);
 
     /* Add a data property whose id is not yet in this scope. */
-    static Shape* addDataProperty(JSContext* cx, HandleNativeObject obj,
-                                  jsid id_, uint32_t slot, unsigned attrs);
     static Shape* addDataProperty(JSContext* cx, HandleNativeObject obj,
                                   HandlePropertyName name, uint32_t slot, unsigned attrs);
 
@@ -897,8 +895,7 @@ class NativeObject : public ShapedObject
      */
     static Shape*
     addDataPropertyInternal(JSContext* cx, HandleNativeObject obj, HandleId id,
-                            uint32_t slot, unsigned attrs, unsigned flags,
-                            ShapeTable::Entry* entry, bool allowDictionary,
+                            uint32_t slot, unsigned attrs, ShapeTable::Entry* entry,
                             const AutoKeepShapeTables& keep);
 
     static Shape*
diff --git a/js/src/vm/Shape-inl.h b/js/src/vm/Shape-inl.h
index d94364867bd96..b533a4ca372b0 100644
--- a/js/src/vm/Shape-inl.h
+++ b/js/src/vm/Shape-inl.h
@@ -392,7 +392,7 @@ Shape::searchNoHashify(Shape* start, jsid id)
 
 /* static */ MOZ_ALWAYS_INLINE Shape*
 NativeObject::addDataProperty(JSContext* cx, HandleNativeObject obj, HandleId id,
-                              uint32_t slot, unsigned attrs, unsigned flags, bool allowDictionary)
+                              uint32_t slot, unsigned attrs)
 {
     MOZ_ASSERT(!JSID_IS_VOID(id));
     MOZ_ASSERT(obj->uninlinedNonProxyIsExtensible());
@@ -407,7 +407,7 @@ NativeObject::addDataProperty(JSContext* cx, HandleNativeObject obj, HandleId id
         entry = &table->search<MaybeAdding::Adding>(id, keep);
     }
 
-    return addDataPropertyInternal(cx, obj, id, slot, attrs, flags, entry, allowDictionary, keep);
+    return addDataPropertyInternal(cx, obj, id, slot, attrs, entry, keep);
 }
 
 /* static */ MOZ_ALWAYS_INLINE Shape*
diff --git a/js/src/vm/Shape.cpp b/js/src/vm/Shape.cpp
index 8d24a61d6a48f..0249f7c3d6cb2 100644
--- a/js/src/vm/Shape.cpp
+++ b/js/src/vm/Shape.cpp
@@ -547,11 +547,8 @@ NativeObject::addAccessorPropertyInternal(JSContext* cx,
 NativeObject::addDataPropertyInternal(JSContext* cx,
                                       HandleNativeObject obj, HandleId id,
                                       uint32_t slot, unsigned attrs,
-                                      unsigned flags, ShapeTable::Entry* entry,
-                                      bool allowDictionary, const AutoKeepShapeTables& keep)
+                                      ShapeTable::Entry* entry, const AutoKeepShapeTables& keep)
 {
-    MOZ_ASSERT_IF(!allowDictionary, !obj->inDictionaryMode());
-
     AutoCheckShapeConsistency check(obj);
 
     /*
@@ -564,10 +561,7 @@ NativeObject::addDataPropertyInternal(JSContext* cx,
             (slot == SHAPE_INVALID_SLOT) ||
             obj->lastProperty()->hasMissingSlot() ||
             (slot == obj->lastProperty()->maybeSlot() + 1);
-        MOZ_ASSERT_IF(!allowDictionary, stableSlot);
-        if (allowDictionary &&
-            (!stableSlot || ShouldConvertToDictionary(obj)))
-        {
+        if (!stableSlot || ShouldConvertToDictionary(obj)) {
             if (!toDictionaryMode(cx, obj))
                 return nullptr;
             table = obj->lastProperty()->maybeTable(keep);
@@ -595,7 +589,7 @@ NativeObject::addDataPropertyInternal(JSContext* cx,
         if (!nbase)
             return nullptr;
 
-        Rooted<StackShape> child(cx, StackShape(nbase, id, slot, attrs, flags));
+        Rooted<StackShape> child(cx, StackShape(nbase, id, slot, attrs, 0));
         shape = getChildProperty(cx, obj, last, &child);
         if (!shape)
             return nullptr;
@@ -817,8 +811,7 @@ NativeObject::putDataProperty(JSContext* cx, HandleNativeObject obj, HandleId id
          */
         MOZ_ASSERT(obj->nonProxyIsExtensible());
 
-        return addDataPropertyInternal(cx, obj, id, SHAPE_INVALID_SLOT, attrs, 0, entry, true,
-                                       keep);
+        return addDataPropertyInternal(cx, obj, id, SHAPE_INVALID_SLOT, attrs, entry, keep);
     }
 
     /* Property exists: search must have returned a valid entry. */
diff --git a/js/src/vm/UnboxedObject.cpp b/js/src/vm/UnboxedObject.cpp
index d8422158301bc..2ed3144bd9a8d 100644
--- a/js/src/vm/UnboxedObject.cpp
+++ b/js/src/vm/UnboxedObject.cpp
@@ -394,9 +394,11 @@ MakeReplacementTemplateObject(JSContext* cx, HandleObjectGroup group, const Unbo
     if (!obj)
         return nullptr;
 
+    RootedId id(cx);
     for (size_t i = 0; i < layout.properties().length(); i++) {
         const UnboxedLayout::Property& property = layout.properties()[i];
-        if (!NativeObject::addDataProperty(cx, obj, NameToId(property.name), i, JSPROP_ENUMERATE))
+        id = NameToId(property.name);
+        if (!NativeObject::addDataProperty(cx, obj, id, i, JSPROP_ENUMERATE))
             return nullptr;
         MOZ_ASSERT(obj->slotSpan() == i + 1);
         MOZ_ASSERT(!obj->inDictionaryMode());