diff --git a/widget/PuppetWidget.cpp b/widget/PuppetWidget.cpp
index 2bd483241c7b..7c0c9dbb7c2f 100644
--- a/widget/PuppetWidget.cpp
+++ b/widget/PuppetWidget.cpp
@@ -697,9 +697,18 @@ PuppetWidget::NotifyIMEOfFocusChange(const IMENotification& aIMENotification)
 
   bool gotFocus = aIMENotification.mMessage == NOTIFY_IME_OF_FOCUS;
   if (gotFocus) {
-    // When IME gets focus, we should initalize all information of the content.
-    if (NS_WARN_IF(!mContentCache.CacheAll(this, &aIMENotification))) {
-      return NS_ERROR_FAILURE;
+    if (mInputContext.mIMEState.mEnabled != IMEState::PLUGIN) {
+      // When IME gets focus, we should initalize all information of the
+      // content.
+      if (NS_WARN_IF(!mContentCache.CacheAll(this, &aIMENotification))) {
+        return NS_ERROR_FAILURE;
+      }
+    } else {
+      // However, if a plugin has focus, only the editor rect information is
+      // available.
+      if (NS_WARN_IF(!mContentCache.CacheEditorRect(this, &aIMENotification))) {
+        return NS_ERROR_FAILURE;
+      }
     }
   } else {
     // When IME loses focus, we don't need to store anything.
@@ -724,7 +733,8 @@ PuppetWidget::NotifyIMEOfCompositionUpdate(
 
   NS_ENSURE_TRUE(mTabChild, NS_ERROR_FAILURE);
 
-  if (NS_WARN_IF(!mContentCache.CacheSelection(this, &aIMENotification))) {
+  if (mInputContext.mIMEState.mEnabled != IMEState::PLUGIN &&
+      NS_WARN_IF(!mContentCache.CacheSelection(this, &aIMENotification))) {
     return NS_ERROR_FAILURE;
   }
   mTabChild->SendNotifyIMECompositionUpdate(mContentCache, aIMENotification);
@@ -769,6 +779,11 @@ PuppetWidget::NotifyIMEOfTextChange(const IMENotification& aIMENotification)
   if (!mTabChild)
     return NS_ERROR_FAILURE;
 
+  // While a plugin has focus, text change notification shouldn't be available.
+  if (NS_WARN_IF(mInputContext.mIMEState.mEnabled == IMEState::PLUGIN)) {
+    return NS_ERROR_FAILURE;
+  }
+
   // FYI: text change notification is the first notification after
   //      a user operation changes the content.  So, we need to modify
   //      the cache as far as possible here.
@@ -803,6 +818,12 @@ PuppetWidget::NotifyIMEOfSelectionChange(
   if (!mTabChild)
     return NS_ERROR_FAILURE;
 
+  // While a plugin has focus, selection change notification shouldn't be
+  // available.
+  if (NS_WARN_IF(mInputContext.mIMEState.mEnabled == IMEState::PLUGIN)) {
+    return NS_ERROR_FAILURE;
+  }
+
   // Note that selection change must be notified after text change if it occurs.
   // Therefore, we don't need to query text content again here.
   mContentCache.SetSelection(
@@ -830,6 +851,13 @@ PuppetWidget::NotifyIMEOfMouseButtonEvent(
     return NS_ERROR_FAILURE;
   }
 
+  // While a plugin has focus, mouse button event notification shouldn't be
+  // available.
+  if (NS_WARN_IF(mInputContext.mIMEState.mEnabled == IMEState::PLUGIN)) {
+    return NS_ERROR_FAILURE;
+  }
+
+
   bool consumedByIME = false;
   if (!mTabChild->SendNotifyIMEMouseButtonEvent(aIMENotification,
                                                 &consumedByIME)) {
@@ -849,7 +877,12 @@ PuppetWidget::NotifyIMEOfPositionChange(const IMENotification& aIMENotification)
     return NS_ERROR_FAILURE;
   }
 
-  if (NS_WARN_IF(!mContentCache.CacheEditorRect(this, &aIMENotification)) ||
+  if (NS_WARN_IF(!mContentCache.CacheEditorRect(this, &aIMENotification))) {
+    return NS_ERROR_FAILURE;
+  }
+  // While a plugin has focus, selection range isn't available.  So, we don't
+  // need to cache it at that time.
+  if (mInputContext.mIMEState.mEnabled != IMEState::PLUGIN &&
       NS_WARN_IF(!mContentCache.CacheSelection(this, &aIMENotification))) {
     return NS_ERROR_FAILURE;
   }