--- a/tools/mbpart.cpp	2019-03-22 10:10:23.242049300 -0400
+++ b/tools/mbpart.cpp	2019-03-22 10:10:26.354738990 -0400
@@ -491,7 +491,7 @@
       rval = mb.write_file(tmp_output_file.str().c_str());
       if (MB_SUCCESS != rval)
       {
-        std::cerr << tmp_output_file << " : failed to write file." << std::endl;
+        std::cerr << tmp_output_file.str() << " : failed to write file." << std::endl;
         std::cerr << "  Error code: " << mb.get_error_string(rval) << " ("
                   << rval << ")" << std::endl;
         std::string errstr;