diff --git a/include/argparse/argparse.hpp b/include/argparse/argparse.hpp
index a66c8ed..d4aec0e 100644
--- a/include/argparse/argparse.hpp
+++ b/include/argparse/argparse.hpp
@@ -46,13 +46,13 @@ SOFTWARE.
 #include <map>
 #include <numeric>
 #include <optional>
+#include <set>
 #include <sstream>
 #include <stdexcept>
 #include <string>
 #include <string_view>
 #include <tuple>
 #include <type_traits>
-#include <unordered_set>
 #include <utility>
 #include <variant>
 #include <vector>
@@ -1419,6 +1419,19 @@ public:
       m_subparser_map.insert_or_assign(it->get().m_program_name, it);
       m_subparser_used.insert_or_assign(it->get().m_program_name, false);
     }
+
+    for (auto &g : other.m_mutually_exclusive_groups) {
+      MutuallyExclusiveGroup group(*this, g.m_required);
+      for (auto &arg : g.m_elements) {
+        // Find argument in argument map and add reference to it
+        // in new group
+        // argument_it = other.m_argument_map.find("name")
+        auto first_name = arg->m_names[0];
+        auto it = m_argument_map.find(first_name);
+        group.m_elements.insert(&(*it->second));
+      }
+      m_mutually_exclusive_groups.push_back(std::move(group));
+    }
   }
 
   ~ArgumentParser() = default;
@@ -1485,7 +1498,7 @@ public:
   private:
     ArgumentParser &m_parent;
     bool m_required{false};
-    std::unordered_set<Argument *> m_elements{};
+    std::set<Argument *> m_elements{};
   };
 
   MutuallyExclusiveGroup &add_mutually_exclusive_group(bool required = false) {
@@ -2087,9 +2100,7 @@ private:
   std::list<std::reference_wrapper<ArgumentParser>> m_subparsers;
   std::map<std::string_view, argument_parser_it> m_subparser_map;
   std::map<std::string_view, bool> m_subparser_used;
-  std::vector<MutuallyExclusiveGroup>
-      m_mutually_exclusive_groups; /// TODO: Add this to the copy/move
-                                   /// constructors
+  std::vector<MutuallyExclusiveGroup> m_mutually_exclusive_groups;
 };
 
 } // namespace argparse
diff --git a/test/test_mutually_exclusive_group.cpp b/test/test_mutually_exclusive_group.cpp
index e83e4f7..493f58a 100644
--- a/test/test_mutually_exclusive_group.cpp
+++ b/test/test_mutually_exclusive_group.cpp
@@ -7,7 +7,8 @@ import argparse;
 
 using doctest::test_suite;
 
-TEST_CASE("User-supplied argument" * test_suite("is_used")) {
+TEST_CASE("Create mutually exclusive group with 2 arguments" *
+          test_suite("mutex_args")) {
   argparse::ArgumentParser program("test");
 
   auto &group = program.add_mutually_exclusive_group();
@@ -16,6 +17,23 @@ TEST_CASE("User-supplied argument" * test_suite("is_used")) {
 
   REQUIRE_THROWS_WITH_AS(
       program.parse_args({"test", "--first", "1", "--second", "2"}),
-      "Argument '--first VAR' not allowed with '--second VAR'",
+      "Argument '--second VAR' not allowed with '--first VAR'",
+      std::runtime_error);
+}
+
+TEST_CASE(
+    "Create mutually exclusive group with 2 arguments, then copy the parser" *
+    test_suite("mutex_args")) {
+  argparse::ArgumentParser program("test");
+
+  auto &group = program.add_mutually_exclusive_group();
+  group.add_argument("--first");
+  group.add_argument("--second");
+
+  auto program_copy(program);
+
+  REQUIRE_THROWS_WITH_AS(
+      program_copy.parse_args({"test", "--first", "1", "--second", "2"}),
+      "Argument '--second VAR' not allowed with '--first VAR'",
       std::runtime_error);
 }
\ No newline at end of file