diff --git a/src/mlpack/methods/ann/layer/lstm.hpp b/src/mlpack/methods/ann/layer/lstm.hpp
index 92c06bad69..1deaf7756d 100644
--- a/src/mlpack/methods/ann/layer/lstm.hpp
+++ b/src/mlpack/methods/ann/layer/lstm.hpp
@@ -108,8 +108,8 @@ class LSTMType : public RecurrentLayer<MatType>
    * @param gy The backpropagated error.
    * @param g The calculated gradient.
    */
-  void Backward(const MatType& input,
-                const MatType& output,
+  void Backward(const MatType& /* input */,
+                const MatType& /* output */,
                 const MatType& gy,
                 MatType& g);