diff --git a/lldb/include/lldb/Core/Broadcaster.h b/lldb/include/lldb/Core/Broadcaster.h
index 64b12ca8a938..6d54b1b43133 100644
--- a/lldb/include/lldb/Core/Broadcaster.h
+++ b/lldb/include/lldb/Core/Broadcaster.h
@@ -419,12 +419,7 @@ public:
     HijackBroadcaster (Listener *listener, uint32_t event_mask = UINT32_MAX);
     
     bool
-    IsHijackedForEvent (uint32_t event_mask)
-    {
-        if (m_hijacking_listeners.size() > 0)
-            return (event_mask & m_hijacking_masks.back()) != 0;
-        return false;
-    }
+    IsHijackedForEvent (uint32_t event_mask);
 
     //------------------------------------------------------------------
     /// Restore the state of the Broadcaster from a previous hijack attempt.
diff --git a/lldb/source/Core/Broadcaster.cpp b/lldb/source/Core/Broadcaster.cpp
index dc37516c29c2..1cbbde20e7f6 100644
--- a/lldb/source/Core/Broadcaster.cpp
+++ b/lldb/source/Core/Broadcaster.cpp
@@ -303,6 +303,16 @@ Broadcaster::HijackBroadcaster (Listener *listener, uint32_t event_mask)
     return true;
 }
 
+bool
+Broadcaster::IsHijackedForEvent (uint32_t event_mask)
+{
+    Mutex::Locker event_types_locker(m_listeners_mutex);
+
+    if (!m_hijacking_listeners.empty())
+        return (event_mask & m_hijacking_masks.back()) != 0;
+    return false;
+}
+
 void
 Broadcaster::RestoreBroadcaster ()
 {