diff --git a/src/mlpack/methods/ann/ffn.hpp b/src/mlpack/methods/ann/ffn.hpp
index dad7128b54..e7c14ead56 100644
--- a/src/mlpack/methods/ann/ffn.hpp
+++ b/src/mlpack/methods/ann/ffn.hpp
@@ -474,7 +474,7 @@ template<typename OutputLayerType,
 struct version<
     mlpack::ann::FFN<OutputLayerType, InitializationRuleType, CustomLayer...>>
 {
-  BOOST_STATIC_CONSTANT(unsigned int, value = 1);
+  BOOST_STATIC_CONSTANT(int, value = 1);
 };
 
 } // namespace serialization
diff --git a/src/mlpack/methods/ann/rnn.hpp b/src/mlpack/methods/ann/rnn.hpp
index c7bb1c9131..c2b05b9db7 100644
--- a/src/mlpack/methods/ann/rnn.hpp
+++ b/src/mlpack/methods/ann/rnn.hpp
@@ -396,7 +396,7 @@ template<typename OutputLayerType,
 struct version<
     mlpack::ann::RNN<OutputLayerType, InitializationRuleType, CustomLayer...>>
 {
-  BOOST_STATIC_CONSTANT(unsigned int, value = 1);
+  BOOST_STATIC_CONSTANT(int, value = 1);
 };
 
 } // namespace serialization