diff --git a/src/cocoa/pen.mm b/src/cocoa/pen.mm
index 5446e50d4c..21c5865c3b 100644
--- a/src/cocoa/pen.mm
+++ b/src/cocoa/pen.mm
@@ -129,6 +129,7 @@ inline wxPenRefData::wxPenRefData(const wxPenRefData& data)
     m_dash = data.m_dash;
     m_stipple = data.m_stipple;
     m_cocoaNSColor = [data.m_cocoaNSColor retain];
+    m_cocoaDash = NULL;
 }
 
 inline void wxPenRefData::FreeCocoaNSColor()