diff --git a/src/mlpack/tests/ann_layer_test.cpp b/src/mlpack/tests/ann_layer_test.cpp
index 942c3f435b..9c46fba8db 100644
--- a/src/mlpack/tests/ann_layer_test.cpp
+++ b/src/mlpack/tests/ann_layer_test.cpp
@@ -324,7 +324,9 @@ BOOST_AUTO_TEST_CASE(BatchNormTest)
 
   arma::mat input = dataset.submat(0, 0, dataset.n_rows-1, 2);
 
-  BatchNorm<> model(input.n_rows);
+  size_t numUnits = input.n_rows;
+
+  BatchNorm<> model(numUnits);
   model.Reset();
 
   // Non-Deteministic Forward Pass Test.