diff --git a/src/gtk/pen.cpp b/src/gtk/pen.cpp
index 0a785a8dee..a0fd6d563b 100644
--- a/src/gtk/pen.cpp
+++ b/src/gtk/pen.cpp
@@ -24,6 +24,7 @@ class wxPenRefData: public wxObjectRefData
   public:
   
     wxPenRefData(void);
+    wxPenRefData(const wxPenRefData& data);
   
     int        m_width;
     int        m_style;
diff --git a/src/gtk1/pen.cpp b/src/gtk1/pen.cpp
index 0a785a8dee..a0fd6d563b 100644
--- a/src/gtk1/pen.cpp
+++ b/src/gtk1/pen.cpp
@@ -24,6 +24,7 @@ class wxPenRefData: public wxObjectRefData
   public:
   
     wxPenRefData(void);
+    wxPenRefData(const wxPenRefData& data);
   
     int        m_width;
     int        m_style;