diff --git a/flang/unittests/Runtime/external-hello.cpp b/flang/unittests/Runtime/external-hello.cpp
--- a/flang/unittests/Runtime/external-hello.cpp
+++ b/flang/unittests/Runtime/external-hello.cpp
@@ -2,6 +2,7 @@
 #include "../../runtime/main.h"
 #include "../../runtime/stop.h"
 #include <cstring>
+#include <limits>
 
 using namespace Fortran::runtime::io;
 
@@ -13,9 +14,9 @@
   IONAME(OutputReal64)(io, 0.0);
   IONAME(OutputReal64)(io, 2.0 / 3.0);
   IONAME(OutputReal64)(io, 1.0e99);
-  IONAME(OutputReal64)(io, 1.0 / 0.0);
-  IONAME(OutputReal64)(io, -1.0 / 0.0);
-  IONAME(OutputReal64)(io, 0.0 / 0.0);
+  IONAME(OutputReal64)(io, std::numeric_limits<double>::infinity());
+  IONAME(OutputReal64)(io, -std::numeric_limits<double>::infinity());
+  IONAME(OutputReal64)(io, std::numeric_limits<double>::quiet_NaN());
   IONAME(OutputComplex64)(io, 123.0, -234.0);
   IONAME(OutputLogical)(io, false);
   IONAME(OutputLogical)(io, true);