diff --git a/src/aui/framemanager.cpp b/src/aui/framemanager.cpp
index 4616efe633..2c85e56551 100644
--- a/src/aui/framemanager.cpp
+++ b/src/aui/framemanager.cpp
@@ -582,6 +582,7 @@ END_EVENT_TABLE()
 wxAuiManager::wxAuiManager(wxWindow* managed_wnd, unsigned int flags)
 {
     m_action = actionNone;
+    m_action_window = NULL;
     m_last_mouse_move = wxPoint();
     m_hover_button = NULL;
     m_art = new wxAuiDefaultDockArt;