diff --git a/gtsam_unstable/linear/LinearConstraint.h b/gtsam_unstable/linear/LinearConstraint.h
index 8cb190016..365c06688 100644
--- a/gtsam_unstable/linear/LinearConstraint.h
+++ b/gtsam_unstable/linear/LinearConstraint.h
@@ -94,11 +94,17 @@ public:
   virtual ~LinearConstraint() {
   }
 
-  // Testable interface
+  /** equals */
   virtual bool equals(const GaussianFactor& lf, double tol = 1e-9) const {
     return Base::equals(lf, tol);
   }
 
+  /** print */
+  virtual void print(const std::string& s = "", const KeyFormatter& formatter =
+      DefaultKeyFormatter) const {
+    Base::print(s, formatter);
+  }
+
   /** Clone this LinearConstraint */
   virtual GaussianFactor::shared_ptr clone() const {
     return boost::static_pointer_cast<GaussianFactor>(