diff --git a/widget/src/windows/nsTextStore.cpp b/widget/src/windows/nsTextStore.cpp
index fdb5277d26a..18687596901 100644
--- a/widget/src/windows/nsTextStore.cpp
+++ b/widget/src/windows/nsTextStore.cpp
@@ -601,6 +601,46 @@ IsSameTextEvent(const nsTextEvent* aEvent1, const nsTextEvent* aEvent2)
                    sizeof(nsTextRange) * aEvent1->rangeCount)));
 }
 
+HRESULT
+nsTextStore::UpdateCompositionExtent(ITfRange* aRangeNew)
+{
+  NS_ENSURE_TRUE(mCompositionView, E_FAIL);
+
+  HRESULT hr;
+  nsRefPtr<ITfCompositionView> pComposition(mCompositionView);
+  nsRefPtr<ITfRange> composingRange(aRangeNew);
+  if (!composingRange) {
+    hr = pComposition->GetRange(getter_AddRefs(composingRange));
+    NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
+  }
+
+  // Get starting offset of the composition
+  LONG compStart = 0, compLength = 0;
+  hr = GetRangeExtent(composingRange, &compStart, &compLength);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
+  if (mCompositionStart != compStart ||
+      mCompositionString.Length() != compLength) {
+    // If the queried composition length is different from the length
+    // of our composition string, OnUpdateComposition is being called
+    // because a part of the original composition was committed.
+    // Reflect that by committing existing composition and starting
+    // a new one. OnEndComposition followed by OnStartComposition
+    // will accomplish this automagically.
+    OnEndComposition(pComposition);
+    OnStartCompositionInternal(pComposition, composingRange, PR_TRUE);
+    PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
+           ("TSF: UpdateCompositionExtent, (reset) range=%ld-%ld\n",
+            compStart, compStart + compLength));
+  } else {
+    mCompositionLength = compLength;
+    PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
+           ("TSF: UpdateCompositionExtent, range=%ld-%ld\n",
+            compStart, compStart + compLength));
+  }
+
+  return S_OK;
+}
+
 HRESULT
 nsTextStore::SendTextEventForCompositionString()
 {
@@ -704,6 +744,10 @@ nsTextStore::SetSelectionInternal(const TS_SELECTION_ACP* pSelection,
          ("TSF: SetSelection, sel=%ld-%ld\n",
           pSelection->acpStart, pSelection->acpEnd));
   if (mCompositionView) {
+    if (aDispatchTextEvent) {
+      HRESULT hr = UpdateCompositionExtent(nsnull);
+      NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
+    }
     // Emulate selection during compositions
     NS_ENSURE_TRUE(pSelection->acpStart >= mCompositionStart &&
                    pSelection->acpEnd <= mCompositionStart +
@@ -1270,29 +1314,8 @@ nsTextStore::OnUpdateComposition(ITfCompositionView* pComposition,
   if (!pRangeNew) // pRangeNew is null when the update is not complete
     return S_OK;
 
-  // Get starting offset of the composition
-  LONG compStart = 0, compLength = 0;
-  HRESULT hr = GetRangeExtent(pRangeNew, &compStart, &compLength);
+  HRESULT hr = UpdateCompositionExtent(pRangeNew);
   NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
-  if (mCompositionStart != compStart ||
-      mCompositionString.Length() != compLength) {
-    // If the queried composition length is different from the length
-    // of our composition string, OnUpdateComposition is being called
-    // because a part of the original composition was committed.
-    // Reflect that by committing existing composition and starting
-    // a new one. OnEndComposition followed by OnStartComposition
-    // will accomplish this automagically.
-    OnEndComposition(pComposition);
-    OnStartCompositionInternal(pComposition, pRangeNew, PR_TRUE);
-    PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
-           ("TSF: OnUpdateComposition, (reset) range=%ld-%ld\n",
-            compStart, compStart + compLength));
-  } else {
-    mCompositionLength = compLength;
-    PR_LOG(sTextStoreLog, PR_LOG_ALWAYS,
-           ("TSF: OnUpdateComposition, range=%ld-%ld\n",
-            compStart, compStart + compLength));
-  }
 
   return SendTextEventForCompositionString();
 }
diff --git a/widget/src/windows/nsTextStore.h b/widget/src/windows/nsTextStore.h
index d66877bb9eb..65b0720a492 100644
--- a/widget/src/windows/nsTextStore.h
+++ b/widget/src/windows/nsTextStore.h
@@ -199,6 +199,7 @@ protected:
   HRESULT  GetDisplayAttribute(ITfProperty* aProperty,
                                ITfRange* aRange,
                                TF_DISPLAYATTRIBUTE* aResult);
+  HRESULT  UpdateCompositionExtent(ITfRange* pRangeNew);
   HRESULT  SendTextEventForCompositionString();
   HRESULT  SaveTextEvent(const nsTextEvent* aEvent);
   nsresult OnCompositionTimer();