diff --git a/freecad/asm3/system.py b/freecad/asm3/system.py
index be871b7..5f2ee3e 100644
--- a/freecad/asm3/system.py
+++ b/freecad/asm3/system.py
@@ -225,7 +225,7 @@ class SystemExtension(object):
                                    pln1.normal, pln2.normal, group)
 
     def addAttachment(self, pln1, pln2, group=0):
-        return self.addPlaneCoincident(0,0,0,False,0,0,0, pln1, pln2, group)
+        return self.addPlaneCoincident(0,0,0,True,0,0,0, pln1, pln2, group)
 
     def addPlaneAlignment(self,d,lockAngle,yaw,pitch,roll,pln1,pln2,group=0):
         if not group: