diff --git a/src/unique_path.cpp b/src/unique_path.cpp
index 1b05c839..93eb4b11 100644
--- a/src/unique_path.cpp
+++ b/src/unique_path.cpp
@@ -111,7 +111,7 @@ void system_crypt_random(void* buf, std::size_t len, boost::system::error_code*
 
   if (!errval)
   {
-    BOOL gen_ok = ::CryptGenRandom(handle, len, static_cast<unsigned char*>(buf));
+    BOOL gen_ok = ::CryptGenRandom(handle, static_cast<DWORD>(len), static_cast<unsigned char*>(buf));
     if (!gen_ok)
       errval = ::GetLastError();
     ::CryptReleaseContext(handle, 0);
diff --git a/src/windows_file_codecvt.cpp b/src/windows_file_codecvt.cpp
index 998db602..99059598 100644
--- a/src/windows_file_codecvt.cpp
+++ b/src/windows_file_codecvt.cpp
@@ -40,7 +40,7 @@
 
     int count;
     if ((count = ::MultiByteToWideChar(codepage, MB_PRECOMPOSED, from,
-      from_end - from, to, to_end - to)) == 0) 
+      static_cast<int>(from_end - from), to, static_cast<int>(to_end - to))) == 0) 
     {
       return error;  // conversion failed
     }
@@ -60,7 +60,7 @@
 
     int count;
     if ((count = ::WideCharToMultiByte(codepage, WC_NO_BEST_FIT_CHARS, from,
-      from_end - from, to, to_end - to, 0, 0)) == 0)
+      static_cast<int>(from_end - from), to, static_cast<int>(to_end - to), 0, 0)) == 0)
     {
       return error;  // conversion failed
     }