diff --git a/packages/CLPBN/horus/ConstraintTree.cpp b/packages/CLPBN/horus/ConstraintTree.cpp
index 07aaf35a3..59705e1e1 100644
--- a/packages/CLPBN/horus/ConstraintTree.cpp
+++ b/packages/CLPBN/horus/ConstraintTree.cpp
@@ -187,9 +187,7 @@ ConstraintTree::ConstraintTree (
 
 ConstraintTree::ConstraintTree (const ConstraintTree& ct)
 {
-  root_       = CTNode::copySubtree (ct.root_);
-  logVars_    = ct.logVars_;
-  logVarSet_  = ct.logVarSet_;
+  *this = ct;
 }
 
 
@@ -875,6 +873,19 @@ ConstraintTree::copyLogVar (LogVar X_1, LogVar X_2)
 
 
 
+ConstraintTree&
+ConstraintTree::operator= (const ConstraintTree& ct)
+{
+  if (this != &ct) {
+    root_      = CTNode::copySubtree (ct.root_);
+    logVars_   = ct.logVars_;
+    logVarSet_ = ct.logVarSet_;
+  }
+  return *this;
+}
+
+
+
 unsigned
 ConstraintTree::countTuples (const CTNode* n) const
 {
diff --git a/packages/CLPBN/horus/ConstraintTree.h b/packages/CLPBN/horus/ConstraintTree.h
index d233a2e97..071a96a5e 100644
--- a/packages/CLPBN/horus/ConstraintTree.h
+++ b/packages/CLPBN/horus/ConstraintTree.h
@@ -199,6 +199,8 @@ class ConstraintTree
     ConstraintTrees ground (LogVar);
 
     void copyLogVar (LogVar,LogVar);
+    
+    ConstraintTree& operator= (const ConstraintTree& ct);
    
   private:
     unsigned countTuples (const CTNode*) const;