diff --git a/mozilla/xpcom/threads/nsTimerImpl.cpp b/mozilla/xpcom/threads/nsTimerImpl.cpp
index 9bf17a9c0f5..c8cf98847a4 100644
--- a/mozilla/xpcom/threads/nsTimerImpl.cpp
+++ b/mozilla/xpcom/threads/nsTimerImpl.cpp
@@ -177,10 +177,7 @@ nsTimerImpl::nsTimerImpl() :
 
 nsTimerImpl::~nsTimerImpl()
 {
-  if (mCallbackType == CALLBACK_TYPE_INTERFACE)
-    NS_RELEASE(mCallback.i);
-  else if (mCallbackType == CALLBACK_TYPE_OBSERVER)
-    NS_RELEASE(mCallback.o);
+  ReleaseCallback();
 }
 
 
@@ -241,6 +238,7 @@ NS_IMETHODIMP nsTimerImpl::InitWithFuncCallback(nsTimerCallbackFunc aFunc,
   if (!gThread)
     return NS_ERROR_FAILURE;
 
+  ReleaseCallback();
   mCallbackType = CALLBACK_TYPE_FUNC;
   mCallback.c = aFunc;
   mClosure = aClosure;
@@ -255,6 +253,7 @@ NS_IMETHODIMP nsTimerImpl::InitWithCallback(nsITimerCallback *aCallback,
   if (!gThread)
     return NS_ERROR_FAILURE;
 
+  ReleaseCallback();
   mCallbackType = CALLBACK_TYPE_INTERFACE;
   mCallback.i = aCallback;
   NS_ADDREF(mCallback.i);
@@ -269,6 +268,7 @@ NS_IMETHODIMP nsTimerImpl::Init(nsIObserver *aObserver,
   if (!gThread)
     return NS_ERROR_FAILURE;
 
+  ReleaseCallback();
   mCallbackType = CALLBACK_TYPE_OBSERVER;
   mCallback.o = aObserver;
   NS_ADDREF(mCallback.o);
diff --git a/mozilla/xpcom/threads/nsTimerImpl.h b/mozilla/xpcom/threads/nsTimerImpl.h
index 90733deeda7..dce1abfe7fd 100644
--- a/mozilla/xpcom/threads/nsTimerImpl.h
+++ b/mozilla/xpcom/threads/nsTimerImpl.h
@@ -42,6 +42,7 @@
 #include "nsVoidArray.h"
 #include "nsIThread.h"
 #include "nsITimerInternal.h"
+#include "nsIObserver.h"
 
 #include "nsCOMPtr.h"
 
@@ -103,6 +104,14 @@ public:
 private:
   nsresult InitCommon(PRUint32 aType, PRUint32 aDelay);
 
+  void ReleaseCallback()
+  {
+    if (mCallbackType == CALLBACK_TYPE_INTERFACE)
+      NS_RELEASE(mCallback.i);
+    else if (mCallbackType == CALLBACK_TYPE_OBSERVER)
+      NS_RELEASE(mCallback.o);
+  }
+
   nsCOMPtr<nsIThread>   mCallingThread;
 
   void *                mClosure;