--- VTK/Common/Core/vtkGenericDataArrayLookupHelper.h	2020-08-04 22:12:01.000000000 +0200
+++ VTK/Common/Core/vtkGenericDataArrayLookupHelper.h	2020-08-29 22:33:06.824012475 +0200
@@ -36,20 +36,20 @@
 template <typename T>
 struct has_NaN<T, true>
 {
-  static bool isnan(T x) { return std::isnan(x); }
+  static bool vtkisnan(T x) { return std::isnan(x); }
 };
 
 template <typename T>
 struct has_NaN<T, false>
 {
-  static bool isnan(T) { return false; }
+  static bool vtkisnan(T) { return false; }
 };
 
 template <typename T>
-bool isnan(T x)
+bool vtkisnan(T x)
 {
   // Select the correct partially specialized type.
-  return has_NaN<T, std::numeric_limits<T>::has_quiet_NaN>::isnan(x);
+  return has_NaN<T, std::numeric_limits<T>::has_quiet_NaN>::vtkisnan(x);
 }
 } // namespace detail
 
@@ -127,7 +127,7 @@
     for (vtkIdType i = 0; i < num; ++i)
     {
       auto value = this->AssociatedArray->GetValue(i);
-      if (::detail::isnan(value))
+      if (::detail::vtkisnan(value))
       {
         NanIndices.push_back(i);
       }
@@ -140,7 +140,7 @@
   std::vector<vtkIdType>* FindIndexVec(ValueType value)
   {
     std::vector<vtkIdType>* indices{ nullptr };
-    if (::detail::isnan(value) && !this->NanIndices.empty())
+    if (::detail::vtkisnan(value) && !this->NanIndices.empty())
     {
       indices = &this->NanIndices;
     }