--- a/editor/libeditor/EditorDOMPoint.h
+++ b/editor/libeditor/EditorDOMPoint.h
@@ -107,21 +107,21 @@ public:
    */
   explicit EditorDOMPointBase(nsINode* aPointedNode)
     : mParent(aPointedNode && aPointedNode->IsContent() ?
                 aPointedNode->GetParentNode() : nullptr)
     , mChild(aPointedNode && aPointedNode->IsContent() ?
                 aPointedNode->AsContent() : nullptr)
     , mIsChildInitialized(false)
   {
+    mIsChildInitialized = aPointedNode && mChild;
     NS_WARNING_ASSERTION(IsSet(),
       "The child is nullptr or doesn't have its parent");
     NS_WARNING_ASSERTION(mChild && mChild->GetParentNode() == mParent,
       "Initializing RangeBoundary with invalid value");
-    mIsChildInitialized = aPointedNode && mChild;
   }
 
   EditorDOMPointBase(nsINode* aContainer,
                      nsIContent* aPointedNode,
                      int32_t aOffset)
     : mParent(aContainer)
     , mChild(aPointedNode)
     , mOffset(mozilla::Some(aOffset))
@@ -426,19 +426,25 @@ public:
     //   If mChild isn't initialized and the offset is 0.
     if (NS_WARN_IF(!mParent)) {
       return false;
     }
     if (!mParent->IsContainerNode()) {
       return !mOffset.value();
     }
     if (mIsChildInitialized) {
-      NS_WARNING_ASSERTION(!mOffset.isSome() || !mOffset.value(),
-        "If offset was initialized, mOffset should be 0");
-      return mParent->GetFirstChild() == mChild;
+      if (mParent->GetFirstChild() == mChild) {
+        NS_WARNING_ASSERTION(!mOffset.isSome() || !mOffset.value(),
+          "If mOffset was initialized, it should be 0");
+        return true;
+      }
+      NS_WARNING_ASSERTION(!mOffset.isSome() ||
+                           mParent->GetChildAt(mOffset.value()) == mChild,
+        "If mOffset and mChild are mismatched");
+      return false;
     }
     MOZ_ASSERT(mOffset.isSome());
     return !mOffset.value();
   }
 
   bool
   IsEndOfContainer() const
   {
@@ -447,20 +453,26 @@ public:
     //   length of the container.
     //   If mChild is initialized and it's nullptr.
     //   If mChild isn't initialized and mOffset is same as the length of the
     //   container.
     if (NS_WARN_IF(!mParent)) {
       return false;
     }
     if (mIsChildInitialized) {
+      if (!mChild) {
+        NS_WARNING_ASSERTION(!mOffset.isSome() ||
+                             mOffset.value() == mParent->Length(),
+          "If mOffset was initialized, it should be length of the container");
+        return true;
+      }
       NS_WARNING_ASSERTION(!mOffset.isSome() ||
-                           mOffset.value() == mParent->Length(),
-        "If offset was initialized, mOffset should be length of the container");
-      return !mChild;
+                           mParent->GetChildAt(mOffset.value()) == mChild,
+        "If mOffset and mChild are mismatched");
+      return false;
     }
     MOZ_ASSERT(mOffset.isSome());
     return mOffset.value() == mParent->Length();
   }
 
   // Convenience methods for switching between the two types
   // of EditorDOMPointBase.
   EditorDOMPointBase<nsINode*, nsIContent*>