Bug: https://bugs.gentoo.org/599564

--- a/Utilities/UnitIO.h
+++ b/Utilities/UnitIO.h
@@ -25,6 +25,9 @@
 
 namespace ThePEG {
 
+using std::isnan;
+using std::isinf;
+
 /**
  * The OUnit< class is used to
  * facilitate output of unitful numbers to a