diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index 9ffced39beff..b6f424c6b87c 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -6434,34 +6434,19 @@ HTMLInputElement::GetSelectionStart(ErrorResult& aRv)
     return Nullable<int32_t>();
   }
 
-  int32_t selStart;
-  nsresult rv = GetSelectionStart(&selStart);
-  if (NS_FAILED(rv)) {
-    aRv.Throw(rv);
-  }
-
-  return Nullable<int32_t>(selStart);
-}
-
-NS_IMETHODIMP
-HTMLInputElement::GetSelectionStart(int32_t* aSelectionStart)
-{
-  NS_ENSURE_ARG_POINTER(aSelectionStart);
-
   int32_t selEnd, selStart;
   nsresult rv = GetSelectionRange(&selStart, &selEnd);
 
   if (NS_FAILED(rv)) {
     nsTextEditorState* state = GetEditorState();
     if (state && state->IsSelectionCached()) {
-      *aSelectionStart = state->GetSelectionProperties().GetStart();
-      return NS_OK;
+      return Nullable<int32_t>(state->GetSelectionProperties().GetStart());
     }
-    return rv;
+    aRv.Throw(rv);
+    return Nullable<int32_t>();
   }
 
-  *aSelectionStart = selStart;
-  return NS_OK;
+  return Nullable<int32_t>(selStart);
 }
 
 void
@@ -6504,15 +6489,6 @@ HTMLInputElement::SetSelectionStart(const Nullable<int32_t>& aSelectionStart,
   aRv = SetSelectionRange(start, end, direction);
 }
 
-NS_IMETHODIMP
-HTMLInputElement::SetSelectionStart(int32_t aSelectionStart)
-{
-  ErrorResult rv;
-  Nullable<int32_t> selStart(aSelectionStart);
-  SetSelectionStart(selStart, rv);
-  return rv.StealNSResult();
-}
-
 Nullable<int32_t>
 HTMLInputElement::GetSelectionEnd(ErrorResult& aRv)
 {
diff --git a/dom/interfaces/html/nsIDOMHTMLInputElement.idl b/dom/interfaces/html/nsIDOMHTMLInputElement.idl
index 0b913571b14a..41345a27f626 100644
--- a/dom/interfaces/html/nsIDOMHTMLInputElement.idl
+++ b/dom/interfaces/html/nsIDOMHTMLInputElement.idl
@@ -84,7 +84,6 @@ interface nsIDOMHTMLInputElement : nsISupports
   void setCustomValidity(in DOMString error);
 
   void select();
-           attribute long                  selectionStart;
            attribute long                  selectionEnd;
   void setSelectionRange(in long selectionStart, in long selectionEnd, [optional] in DOMString direction);
            attribute DOMString             selectionDirection;
diff --git a/toolkit/components/satchel/nsFormFillController.cpp b/toolkit/components/satchel/nsFormFillController.cpp
index be3b2ca4934d..ced04cd6ef54 100644
--- a/toolkit/components/satchel/nsFormFillController.cpp
+++ b/toolkit/components/satchel/nsFormFillController.cpp
@@ -602,8 +602,20 @@ nsFormFillController::SetTextValueWithReason(const nsAString & aTextValue,
 NS_IMETHODIMP
 nsFormFillController::GetSelectionStart(int32_t *aSelectionStart)
 {
-  if (mFocusedInput)
-    mFocusedInput->GetSelectionStart(aSelectionStart);
+  nsCOMPtr<nsIContent> content = do_QueryInterface(mFocusedInput);
+  if (!content) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  ErrorResult rv;
+  Nullable<int32_t> start =
+    HTMLInputElement::FromContent(content)->GetSelectionStart(rv);
+  if (NS_FAILED(rv)) {
+    return rv.StealNSResult();
+  }
+  if (start.IsNull()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  *aSelectionStart = start.Value();
   return NS_OK;
 }