diff --git a/gtsam/linear/HessianFactor.h b/gtsam/linear/HessianFactor.h
index cf187d371..9fd62fed6 100644
--- a/gtsam/linear/HessianFactor.h
+++ b/gtsam/linear/HessianFactor.h
@@ -51,6 +51,7 @@ namespace gtsam {
   };
   class Scatter : public FastMap<Index, SlotEntry> {
   public:
+    Scatter() {}
     Scatter(const FactorGraph<GaussianFactor>& gfg);
   };