diff --git a/editor/libeditor/html/nsHTMLEditRules.cpp b/editor/libeditor/html/nsHTMLEditRules.cpp
index b8ed9e948ecb..637e06581b3b 100644
--- a/editor/libeditor/html/nsHTMLEditRules.cpp
+++ b/editor/libeditor/html/nsHTMLEditRules.cpp
@@ -274,6 +274,9 @@ nsHTMLEditRules::Init(nsPlaintextEditor *aEditor)
 NS_IMETHODIMP
 nsHTMLEditRules::DetachEditor()
 {
+  if (mHTMLEditor) {
+    mHTMLEditor->RemoveEditActionListener(this);
+  }
   mHTMLEditor = nullptr;
   return nsTextEditRules::DetachEditor();
 }
diff --git a/editor/libeditor/html/nsHTMLEditor.cpp b/editor/libeditor/html/nsHTMLEditor.cpp
index 0bae02cc8053..e56ebd08137a 100644
--- a/editor/libeditor/html/nsHTMLEditor.cpp
+++ b/editor/libeditor/html/nsHTMLEditor.cpp
@@ -484,6 +484,7 @@ nsHTMLEditor::SetFlags(uint32_t aFlags)
 NS_IMETHODIMP
 nsHTMLEditor::InitRules()
 {
+  MOZ_ASSERT(!mRules);
   // instantiate the rules for the html editor
   mRules = new nsHTMLEditRules();
   return mRules->Init(static_cast<nsPlaintextEditor*>(this));
diff --git a/editor/libeditor/text/nsPlaintextEditor.cpp b/editor/libeditor/text/nsPlaintextEditor.cpp
index 93648859e0ad..05aaefbeb62b 100644
--- a/editor/libeditor/text/nsPlaintextEditor.cpp
+++ b/editor/libeditor/text/nsPlaintextEditor.cpp
@@ -121,6 +121,10 @@ NS_IMETHODIMP nsPlaintextEditor::Init(nsIDOMDocument *aDoc,
   NS_ENSURE_TRUE(aDoc, NS_ERROR_NULL_POINTER);
   
   nsresult res = NS_OK, rulesRes = NS_OK;
+  if (mRules) {
+    mRules->DetachEditor();
+    mRules = nullptr;
+  }
   
   if (1)
   {
@@ -313,6 +317,7 @@ nsPlaintextEditor::UpdateMetaCharset(nsIDOMDocument* aDocument,
 
 NS_IMETHODIMP nsPlaintextEditor::InitRules()
 {
+  MOZ_ASSERT(!mRules);
   // instantiate the rules for this text editor
   mRules = new nsTextEditRules();
   return mRules->Init(this);