diff --git a/include/behaviortree_cpp_v3/basic_types.h b/include/behaviortree_cpp_v3/basic_types.h
index edfa7aa4b..e4ac2465b 100644
--- a/include/behaviortree_cpp_v3/basic_types.h
+++ b/include/behaviortree_cpp_v3/basic_types.h
@@ -5,7 +5,6 @@
 #include <vector>
 #include <sstream>
 #include <unordered_map>
-#include <unordered_set>
 #include <typeinfo>
 #include <functional>
 #include <chrono>
@@ -216,7 +215,7 @@ using Optional = nonstd::expected<T, std::string>;
  * */
 using Result = Optional<void>;
 
-const std::unordered_set<std::string> ReservedPortNames = {"ID", "name", "_description"};
+static const std::array<std::string, 3> ReservedPortNames = {"ID", "name", "_description"};
 
 class PortInfo
 {
@@ -271,7 +270,7 @@ std::pair<std::string, PortInfo> CreatePort(PortDirection direction, StringView
                                             StringView description = {})
 {
   auto sname = static_cast<std::string>(name);
-  if (ReservedPortNames.count(sname) != 0)
+  if (std::count(ReservedPortNames.begin(), ReservedPortNames.end(), sname) != 0)
   {
     throw std::runtime_error("A port can not use a reserved name. See ReservedPortNames");
   }
diff --git a/src/xml_parsing.cpp b/src/xml_parsing.cpp
index da3aa9d17..fe8d683ad 100644
--- a/src/xml_parsing.cpp
+++ b/src/xml_parsing.cpp
@@ -523,7 +523,7 @@ TreeNode::Ptr XMLParser::Pimpl::createNodeFromXML(const XMLElement* element,
     for (const XMLAttribute* att = element->FirstAttribute(); att; att = att->Next())
     {
       const std::string attribute_name = att->Name();
-      if (ReservedPortNames.count(attribute_name) == 0)
+      if (std::count(ReservedPortNames.begin(), ReservedPortNames.end(), attribute_name) == 0)
       {
         port_remap[attribute_name] = att->Value();
       }
@@ -699,7 +699,7 @@ void BT::XMLParser::Pimpl::recursivelyCreateTree(const std::string& tree_ID,
           for (const XMLAttribute* attr = element->FirstAttribute(); attr != nullptr;
                attr = attr->Next())
           {
-            if (ReservedPortNames.count(attr->Name()) == 0)
+            if (std::count(ReservedPortNames.begin(), ReservedPortNames.end(), attr->Name()) == 0)
             {
               new_bb->addSubtreeRemapping(attr->Name(), attr->Value());
             }
@@ -720,7 +720,7 @@ void BT::XMLParser::Pimpl::recursivelyCreateTree(const std::string& tree_ID,
           const char* attr_name = attr->Name();
           const char* attr_value = attr->Value();
 
-          if (ReservedPortNames.count(attr->Name()) != 0)
+          if (std::count(ReservedPortNames.begin(), ReservedPortNames.end(), attr->Name()) != 0)
           {
             continue;
           }
@@ -779,7 +779,7 @@ void XMLParser::Pimpl::getPortsRecursively(const XMLElement* element,
   {
     const char* attr_name = attr->Name();
     const char* attr_value = attr->Value();
-    if (ReservedPortNames.count(attr_name) == 0 &&
+    if (std::count(ReservedPortNames.begin(), ReservedPortNames.end(), attr_name) == 0 &&
         TreeNode::isBlackboardPointer(attr_value))
     {
       auto port_name = TreeNode::stripBlackboardPointer(attr_value);