diff --git a/test/AnnoyingScalar.h b/test/AnnoyingScalar.h
index 4362de263..dc20d43a7 100644
--- a/test/AnnoyingScalar.h
+++ b/test/AnnoyingScalar.h
@@ -140,6 +140,11 @@ EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
 bool (isfinite)(const AnnoyingScalar& x) {
   return (numext::isfinite)(*x.v);
 }
+template<>
+EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE
+bool (isnan)(const AnnoyingScalar& x) {
+  return (numext::isnan)(*x.v);
+}
 }
 
 namespace internal {