diff --git a/mozilla/xpcom/threads/nsThread.cpp b/mozilla/xpcom/threads/nsThread.cpp
index 7f4948f8923..8a6f1113f07 100644
--- a/mozilla/xpcom/threads/nsThread.cpp
+++ b/mozilla/xpcom/threads/nsThread.cpp
@@ -165,6 +165,13 @@ public:
       mon.Wait();
   }
 
+  // This method needs to be public to support older compilers (xlC_r on AIX).
+  // It should be called directly as this class type is reference counted.
+  virtual ~nsThreadStartupEvent() {
+    if (mMon)
+      nsAutoMonitor::DestroyMonitor(mMon);
+  }
+
 private:
   NS_IMETHOD Run() {
     nsAutoMonitor mon(mMon);
@@ -178,11 +185,6 @@ private:
     , mInitialized(PR_FALSE) {
   }
 
-  virtual ~nsThreadStartupEvent() {
-    if (mMon)
-      nsAutoMonitor::DestroyMonitor(mMon);
-  }
-
   PRMonitor *mMon;
   PRBool     mInitialized;
 };