diff --git a/test_conformance/basic/test_explicit_s2v.cpp b/test_conformance/basic/test_explicit_s2v.cpp
index ea09d13a5..067afb435 100644
--- a/test_conformance/basic/test_explicit_s2v.cpp
+++ b/test_conformance/basic/test_explicit_s2v.cpp
@@ -15,7 +15,6 @@
 //
 #include <cmath>
 using std::isnan;
-#define isnan isnan
 #include "harness/compat.h"
 
 #include <stdio.h>