diff --git a/include/fc/filesystem.hpp b/include/fc/filesystem.hpp
index 3661813..1bc565f 100644
--- a/include/fc/filesystem.hpp
+++ b/include/fc/filesystem.hpp
@@ -66,7 +66,11 @@ namespace fc {
       static char    separator_char;
 
     private:
+    #ifdef _WIN64
+      fwd<boost::filesystem::path,40> _p; 
+    #else
       fwd<boost::filesystem::path,32> _p; 
+    #endif
   };
 
   class directory_iterator {
diff --git a/include/fc/interprocess/file_mapping.hpp b/include/fc/interprocess/file_mapping.hpp
index 051dece..e6b6817 100644
--- a/include/fc/interprocess/file_mapping.hpp
+++ b/include/fc/interprocess/file_mapping.hpp
@@ -21,7 +21,11 @@ namespace fc {
       ~file_mapping();
     private:
       friend class mapped_region;
+    #ifdef _WIN64
+      fc::fwd<boost::interprocess::file_mapping,0x38> my;
+    #else
       fc::fwd<boost::interprocess::file_mapping,0x24> my;
+    #endif
   };
 
   class mapped_region {
diff --git a/include/fc/network/tcp_socket.hpp b/include/fc/network/tcp_socket.hpp
index 05adb2d..b808f24 100644
--- a/include/fc/network/tcp_socket.hpp
+++ b/include/fc/network/tcp_socket.hpp
@@ -32,7 +32,11 @@ namespace fc {
     private:
       friend class tcp_server;
       class impl;
+      #ifdef _WIN64
+      fc::fwd<impl,0x68> my;
+      #else
       fc::fwd<impl,0x44> my;
+      #endif
   };
   typedef std::shared_ptr<tcp_socket> tcp_socket_ptr;