diff --git a/src/mlpack/methods/ann/layer/layer_types.hpp b/src/mlpack/methods/ann/layer/layer_types.hpp
index 39cd3d0cf8..48e8eed0d5 100644
--- a/src/mlpack/methods/ann/layer/layer_types.hpp
+++ b/src/mlpack/methods/ann/layer/layer_types.hpp
@@ -12,7 +12,7 @@
 #ifndef MLPACK_METHODS_ANN_LAYER_LAYER_TYPES_HPP
 #define MLPACK_METHODS_ANN_LAYER_LAYER_TYPES_HPP
 
-// Increase
+// Increase boost:variant size
 #define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
 #define BOOST_MPL_LIMIT_LIST_SIZE 50