diff --git a/src/mlpack/methods/ann/layer/leaky_relu.hpp b/src/mlpack/methods/ann/layer/leaky_relu.hpp
index 8cb4485707..17ee992b61 100644
--- a/src/mlpack/methods/ann/layer/leaky_relu.hpp
+++ b/src/mlpack/methods/ann/layer/leaky_relu.hpp
@@ -84,7 +84,7 @@ class LeakyReLUType : public Layer<MatType>
    * @param g The calculated gradient.
    */
   void Backward(const MatType& input,
-                const MatType& output,
+                const MatType& /* output */,
                 const MatType& gy,
                 MatType& g);