diff --git a/ex4/nnCostFunction.m b/ex4/nnCostFunction.m
index 6a5f55c..3e172c7 100644
--- a/ex4/nnCostFunction.m
+++ b/ex4/nnCostFunction.m
@@ -124,12 +124,16 @@ Theta1_grad = D_1;
 
 % Note: Theta1/2 are matrixes here, we want all their rows, but skip their
 % first column (not regularizing the bias term).
-regularization_term = lambda/(2*m) * ...
+J_regularization_term = lambda/(2*m) * ...
                       (sum(sum(Theta1(:,2:end).^2)) ...
                        + sum(sum(Theta2(:,2:end).^2)));
-assert(size(regularization_term) == [1 1]);
+assert(size(J_regularization_term) == [1 1]);
+J += J_regularization_term;
 
-J += regularization_term;
+Theta2_grad_regularization_term = lambda/m * [zeros(size(Theta2, 1), 1) Theta2(:,2:end)];
+Theta1_grad_regularization_term = lambda/m * [zeros(size(Theta1, 1), 1) Theta1(:,2:end)];
+Theta2_grad += Theta2_grad_regularization_term;
+Theta1_grad += Theta1_grad_regularization_term;
 
 % -------------------------------------------------------------