diff --git a/CHANGES b/CHANGES
index 268a804..81c8b67 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,6 @@
-Version 3.3.1-dev
------------------
+Version 3.3.1 [12 Sep 2023]
+---------------------------
+- Stop using the std::iterator deprecated in C++17.
 
 
 Version 3.3.0 [13 Sep 2022]
diff --git a/gen/template/utf16.h b/gen/template/utf16.h
index 2ab03e8..6498a5e 100644
--- a/gen/template/utf16.h
+++ b/gen/template/utf16.h
@@ -112,8 +112,13 @@ void utf16::decode(const std::u16string& str, std::u32string& decoded) {
   decode(str.c_str(), decoded);
 }
 
-class utf16::string_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf16::string_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char16_t* str) : codepoint(0), next(str) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next) {}
   iterator& operator++() { if (next) { codepoint = decode(next); if (!codepoint) next = nullptr; } return *this; }
@@ -144,8 +149,13 @@ utf16::string_decoder utf16::decoder(const std::u16string& str) {
   return string_decoder(str.c_str());
 }
 
-class utf16::buffer_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf16::buffer_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char16_t* str, size_t len) : codepoint(0), next(str), len(len) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next), len(it.len) {}
   iterator& operator++() { if (!len) next = nullptr; if (next) codepoint = decode(next, len); return *this; }
diff --git a/gen/template/utf8.h b/gen/template/utf8.h
index 2dbdead..924c358 100644
--- a/gen/template/utf8.h
+++ b/gen/template/utf8.h
@@ -144,8 +144,13 @@ void utf8::decode(const std::string& str, std::u32string& decoded) {
   decode(str.c_str(), decoded);
 }
 
-class utf8::string_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf8::string_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char* str) : codepoint(0), next(str) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next) {}
   iterator& operator++() { if (next) { codepoint = decode(next); if (!codepoint) next = nullptr; } return *this; }
@@ -176,8 +181,13 @@ utf8::string_decoder utf8::decoder(const std::string& str) {
   return string_decoder(str.c_str());
 }
 
-class utf8::buffer_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf8::buffer_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char* str, size_t len) : codepoint(0), next(str), len(len) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next), len(it.len) {}
   iterator& operator++() { if (!len) next = nullptr; if (next) codepoint = decode(next, len); return *this; }
diff --git a/unilib/utf16.h b/unilib/utf16.h
index e54221e..cd80a3f 100644
--- a/unilib/utf16.h
+++ b/unilib/utf16.h
@@ -112,8 +112,13 @@ void utf16::decode(const std::u16string& str, std::u32string& decoded) {
   decode(str.c_str(), decoded);
 }
 
-class utf16::string_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf16::string_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char16_t* str) : codepoint(0), next(str) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next) {}
   iterator& operator++() { if (next) { codepoint = decode(next); if (!codepoint) next = nullptr; } return *this; }
@@ -144,8 +149,13 @@ utf16::string_decoder utf16::decoder(const std::u16string& str) {
   return string_decoder(str.c_str());
 }
 
-class utf16::buffer_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf16::buffer_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char16_t* str, size_t len) : codepoint(0), next(str), len(len) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next), len(it.len) {}
   iterator& operator++() { if (!len) next = nullptr; if (next) codepoint = decode(next, len); return *this; }
diff --git a/unilib/utf8.h b/unilib/utf8.h
index fe23e5a..46062cf 100644
--- a/unilib/utf8.h
+++ b/unilib/utf8.h
@@ -144,8 +144,13 @@ void utf8::decode(const std::string& str, std::u32string& decoded) {
   decode(str.c_str(), decoded);
 }
 
-class utf8::string_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf8::string_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char* str) : codepoint(0), next(str) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next) {}
   iterator& operator++() { if (next) { codepoint = decode(next); if (!codepoint) next = nullptr; } return *this; }
@@ -176,8 +181,13 @@ utf8::string_decoder utf8::decoder(const std::string& str) {
   return string_decoder(str.c_str());
 }
 
-class utf8::buffer_decoder::iterator : public std::iterator<std::input_iterator_tag, char32_t> {
+class utf8::buffer_decoder::iterator {
  public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = char32_t;
+  using difference_type = ptrdiff_t;
+  using pointer = char32_t*;
+  using reference = char32_t&;
   iterator(const char* str, size_t len) : codepoint(0), next(str), len(len) { operator++(); }
   iterator(const iterator& it) : codepoint(it.codepoint), next(it.next), len(it.len) {}
   iterator& operator++() { if (!len) next = nullptr; if (next) codepoint = decode(next, len); return *this; }