diff --git a/include/ctpg/ctpg.hpp b/include/ctpg/ctpg.hpp
index 04b46cc..c26daa2 100644
--- a/include/ctpg/ctpg.hpp
+++ b/include/ctpg/ctpg.hpp
@@ -124,8 +124,8 @@ namespace stdex
             constexpr it_type* cast() { return static_cast<it_type*>(this); }
             constexpr const it_type* cast() const { return static_cast<const it_type*>(this); }
 
-            constexpr bool operator == (const it_type& other) const { return cast()->ptr == other.ptr; }
-            constexpr bool operator != (const it_type& other) const { return cast()->ptr != other.ptr; }
+            constexpr friend bool operator == (it_type const& a, it_type const& b) { return a.cast()->ptr == b.cast()->ptr; }
+            constexpr friend bool operator != (it_type const& a, it_type const& b) { return a.cast()->ptr != b.cast()->ptr; }
             constexpr it_type operator - (size_type amount) const { return it_type{ cast()->ptr - amount }; }
             constexpr size_type operator - (const it_type& other) const { return size_type(cast()->ptr - other.ptr); }
             constexpr it_type operator + (size_type amount) const { return it_type{ cast()->ptr + amount }; }
diff --git a/tests/list_helpers.cpp b/tests/list_helpers.cpp
index 2a56542..13ae722 100644
--- a/tests/list_helpers.cpp
+++ b/tests/list_helpers.cpp
@@ -38,6 +38,7 @@ namespace test
 {
     struct non_copyable_thing
     {
+        non_copyable_thing() = default;
         non_copyable_thing(const non_copyable_thing&) = delete;
         non_copyable_thing& operator = (const non_copyable_thing&) = delete;
 
@@ -87,4 +88,4 @@ TEST_CASE("construct", "[list helpers]")
 
     REQUIRE(result.has_value());
     REQUIRE(result.value().size() == 4);
-}
\ No newline at end of file
+}