diff --git a/src/OpenMesh/Core/IO/SR_binary_spec.hh b/src/OpenMesh/Core/IO/SR_binary_spec.hh
index 690fdc0e..6777e8a6 100644
--- a/src/OpenMesh/Core/IO/SR_binary_spec.hh
+++ b/src/OpenMesh/Core/IO/SR_binary_spec.hh
@@ -337,7 +337,7 @@ struct binary< std::vector< T >, typename std::enable_if<std::is_default_constru
   {
     if(binary<T>::size_of() != IO::UnknownSize)
     {
-      unsigned int   N     = _v.size();
+      unsigned int N = static_cast<unsigned int>(_v.size());
       auto res = binary<T>::size_of()*_v.size() + (_store_size? sizeof(decltype(N)) : 0);
       return res;
     }
@@ -359,7 +359,7 @@ struct binary< std::vector< T >, typename std::enable_if<std::is_default_constru
     size_t bytes=0;
     if(_store_size)
     {
-      unsigned int N = _v.size();
+      unsigned int N = static_cast<unsigned int>(_v.size());
       bytes += binary<unsigned int>::store( _os, N, _swap );
     }
     if (_swap)
diff --git a/src/OpenMesh/Core/IO/SR_binary_vector_of_bool.inl b/src/OpenMesh/Core/IO/SR_binary_vector_of_bool.inl
index 6a8c8ceb..2896bb47 100644
--- a/src/OpenMesh/Core/IO/SR_binary_vector_of_bool.inl
+++ b/src/OpenMesh/Core/IO/SR_binary_vector_of_bool.inl
@@ -25,7 +25,7 @@ template <> struct binary< std::vector<bool> >
 
     if(_store_size)
     {
-      unsigned int size_N = _v.size();
+      unsigned int size_N = static_cast<unsigned int>(_v.size());
       bytes += binary<unsigned int>::store( _ostr, size_N, _swap );
     }