Index: libs/iostreams/src/mapped_file.cpp
===================================================================
--- libs/iostreams/src/mapped_file.cpp	(revision 59992)
+++ libs/iostreams/src/mapped_file.cpp	(working copy)
@@ -197,8 +197,10 @@
     if (p.new_file_size != 0 && !readonly) {
         LONG sizehigh = (p.new_file_size >> (sizeof(LONG) * 8));
         LONG sizelow = (p.new_file_size & 0xffffffff);
-        ::SetFilePointer(handle_, sizelow, &sizehigh, FILE_BEGIN);
-        if (::GetLastError() != NO_ERROR || !::SetEndOfFile(handle_))
+        DWORD result = ::SetFilePointer(handle_, sizelow, &sizehigh, FILE_BEGIN);
+        if ( result == INVALID_SET_FILE_POINTER 
+               && ::GetLastError() != NO_ERROR 
+               || !::SetEndOfFile(handle_))
             cleanup_and_throw("failed setting file size");
     }