diff --git a/include/ss/parser.hpp b/include/ss/parser.hpp
index 19ca4cd..11ee763 100644
--- a/include/ss/parser.hpp
+++ b/include/ss/parser.hpp
@@ -89,7 +89,6 @@ public:
         return valid() ? reader_.line_number_ - 1 : 0;
     }
 
-    // TODO append file_name and line number to exception
     template <typename T, typename... Ts>
     no_void_validator_tup_t<T, Ts...> get_next() {
         std::optional<std::string> error;
@@ -209,12 +208,15 @@ public:
             using value = std::conditional_t<get_object, T,
                                              no_void_validator_tup_t<T, Ts...>>;
 
-            iterator() : parser_{nullptr} {
+            iterator() : parser_{nullptr}, value_{} {
             }
 
-            iterator(parser<Options...>* parser) : parser_{parser} {
+            iterator(parser<Options...>* parser) : parser_{parser}, value_{} {
             }
 
+            iterator(const iterator& other) = default;
+            iterator(iterator&& other) = default;
+
             value& operator*() {
                 return value_;
             }
@@ -224,7 +226,7 @@ public:
             }
 
             iterator& operator++() {
-                if (parser_->eof()) {
+                if (!parser_ || parser_->eof()) {
                     parser_ = nullptr;
                 } else {
                     if constexpr (get_object) {
@@ -253,8 +255,8 @@ public:
             }
 
         private:
-            value value_;
             parser<Options...>* parser_;
+            value value_;
         };
 
         iterable(parser<Options...>* parser) : parser_{parser} {
@@ -465,7 +467,14 @@ private:
         std::string raw_header_copy = raw_header_;
         splitter.split(raw_header_copy.data(), reader_.delim_);
         for (const auto& [begin, end] : splitter.split_data_) {
-            header_.emplace_back(begin, end);
+            std::string field{begin, end};
+            if (std::find(header_.begin(), header_.end(), field) !=
+                header_.end()) {
+                handle_error_invalid_header(field);
+                header_.clear();
+                return;
+            }
+            header_.push_back(std::move(field));
         }
     }
 
@@ -597,6 +606,19 @@ private:
         }
     }
 
+    void handle_error_invalid_header(const std::string& field) {
+        constexpr static auto error_msg = "header contains duplicates: ";
+
+        if constexpr (string_error) {
+            error_.clear();
+            error_.append(error_msg).append(error_msg);
+        } else if constexpr (throw_on_error) {
+            throw ss::exception{error_msg + field};
+        } else {
+            error_ = true;
+        }
+    }
+
     void decorate_rethrow(const ss::exception& e) const {
         static_assert(throw_on_error,
                       "throw_on_error needs to be enabled to use this method");
diff --git a/test/test_parser.cpp b/test/test_parser.cpp
index 1e3bc23..40b5969 100644
--- a/test/test_parser.cpp
+++ b/test/test_parser.cpp
@@ -1286,6 +1286,9 @@ void test_invalid_fields(const std::vector<std::string>& lines,
 TEST_CASE("parser test invalid header fields usage") {
     test_invalid_fields({"Int,String,Double", "1,hi,2.34"},
                         {"Int", "String", "Double"});
+
+    test_invalid_fields({"Int,Int,Int", "1,2,3"},
+                        {"Int", "Int", "Int"});
 }
 
 template <typename... Ts>