diff --git a/lang/c++/impl/FileStream.cc b/lang/c++/impl/FileStream.cc
index 63699682fe0..ba78f1ab38c 100644
--- a/lang/c++/impl/FileStream.cc
+++ b/lang/c++/impl/FileStream.cc
@@ -51,7 +51,7 @@ struct FileBufferCopyIn : public BufferCopyIn {
 #ifdef _WIN32
     HANDLE h_;
     FileBufferCopyIn(const char* filename) :
-        h_(::CreateFile(filename, GENERIC_READ, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
+        h_(::CreateFileA(filename, GENERIC_READ, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
         if (h_ == INVALID_HANDLE_VALUE) {
             throw Exception(boost::format("Cannot open file: %1%") % ::GetLastError());
         }
@@ -220,7 +220,7 @@ struct FileBufferCopyOut : public BufferCopyOut {
 #ifdef _WIN32
     HANDLE h_;
     FileBufferCopyOut(const char* filename) :
-        h_(::CreateFile(filename, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
+        h_(::CreateFileA(filename, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL)) {
         if (h_ == INVALID_HANDLE_VALUE) {
             throw Exception(boost::format("Cannot open file: %1%") % ::GetLastError());
         }