diff --git a/CHANGELOG b/CHANGELOG
index 217ffba..7c85c2b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+v0.5.4 (released May 15, 2019):
+
+- Fixed an unlikely crash in the C tokenizer when interrupted while parsing
+  a heading.
+
 v0.5.3 (released March 30, 2019):
 
 - Fixed manual construction of Node objects, previously unsupported. (#214)
diff --git a/appveyor.yml b/appveyor.yml
index 067bffb..3d738e4 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,6 +1,6 @@
 # This config file is used by appveyor.com to build Windows release binaries
 
-version: 0.5.3-b{build}
+version: 0.5.4-b{build}
 
 branches:
   only:
diff --git a/docs/changelog.rst b/docs/changelog.rst
index afdddd6..808e9b9 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,6 +1,15 @@
 Changelog
 =========
 
+v0.5.4
+------
+
+`Released May 15, 2019 <https://github.com/earwig/mwparserfromhell/tree/v0.5.4>`_
+(`changes <https://github.com/earwig/mwparserfromhell/compare/v0.5.3...v0.5.4>`__):
+
+- Fixed an unlikely crash in the C tokenizer when interrupted while parsing
+  a heading.
+
 v0.5.3
 ------
 
diff --git a/mwparserfromhell/__init__.py b/mwparserfromhell/__init__.py
index eefe79a..4e4d440 100644
--- a/mwparserfromhell/__init__.py
+++ b/mwparserfromhell/__init__.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8  -*-
 #
-# Copyright (C) 2012-2018 Ben Kurtovic <ben.kurtovic@gmail.com>
+# Copyright (C) 2012-2019 Ben Kurtovic <ben.kurtovic@gmail.com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -27,9 +27,9 @@ outrageously powerful parser for `MediaWiki <http://mediawiki.org>`_ wikicode.
 """
 
 __author__ = "Ben Kurtovic"
-__copyright__ = "Copyright (C) 2012-2018 Ben Kurtovic"
+__copyright__ = "Copyright (C) 2012-2019 Ben Kurtovic"
 __license__ = "MIT License"
-__version__ = "0.5.3"
+__version__ = "0.5.4"
 __email__ = "ben.kurtovic@gmail.com"
 
 from . import (compat, definitions, nodes, parser, smart_list, string_mixin,
diff --git a/mwparserfromhell/parser/ctokenizer/tok_parse.c b/mwparserfromhell/parser/ctokenizer/tok_parse.c
index ab46252..c32e48c 100644
--- a/mwparserfromhell/parser/ctokenizer/tok_parse.c
+++ b/mwparserfromhell/parser/ctokenizer/tok_parse.c
@@ -813,6 +813,9 @@ static int Tokenizer_parse_heading(Tokenizer* self)
         self->global ^= GL_HEADING;
         return 0;
     }
+    if (!heading) {
+        return -1;
+    }
 #ifdef IS_PY3K
     level = PyLong_FromSsize_t(heading->level);
 #else
@@ -892,6 +895,9 @@ static HeadingData* Tokenizer_handle_heading_end(Tokenizer* self)
         self->head = reset + best - 1;
     }
     else {
+        if (!after) {
+            return NULL;
+        }
         for (i = 0; i < best; i++) {
             if (Tokenizer_emit_char(self, '=')) {
                 Py_DECREF(after->title);