diff --git a/gtsam_unstable/nonlinear/Expression-inl.h b/gtsam_unstable/nonlinear/Expression-inl.h
index c40dfb405..5ee1ca272 100644
--- a/gtsam_unstable/nonlinear/Expression-inl.h
+++ b/gtsam_unstable/nonlinear/Expression-inl.h
@@ -370,7 +370,7 @@ public:
 
   /// Move terms to array, destroys content
   void move(std::vector<Matrix>& H) {
-    assert(H.size()==jacobains.size());
+    assert(H.size()==jacobians_.size());
     size_t j = 0;
     JacobianMap::iterator it = jacobians_.begin();
     for (; it != jacobians_.end(); ++it)