diff --git a/DataTree.cc b/DataTree.cc
index f151fa3a..6b30f1eb 100644
--- a/DataTree.cc
+++ b/DataTree.cc
@@ -634,6 +634,9 @@ DataTree::writePowerDeriv(ostream &output, bool use_dll) const
            << " */" << endl
            << "double getPowerDeriv(double x, double p, int k)" << endl
            << "{" << endl
+           << "#ifdef _MSC_VER" << endl
+           << "# define nearbyint(x) (fabs((x)-floor(x)) < fabs((x)-ceil(x)) ? floor(x) : ceil(x))" << endl
+           << "#endif" << endl
            << "  if ( fabs(x) < " << NEAR_ZERO << " && p > 0 && k >= p && fabs(p-nearbyint(p)) < " << NEAR_ZERO << " )" << endl
            << "    return 0.0;" << endl
            << "  else" << endl