diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70d85e5..c6cfb16 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,17 @@
-Version 4.0.5-dev
+Version 4.1.0-dev
 -----------------
 
-Nothing yet.
+### Added
+
+* Added support for PHP 7.3 flexible heredoc/nowdoc strings, completing support for PHP 7.3. There
+  are two caveats for this feature:
+   * In some rare, pathological cases flexible heredoc/nowdoc strings change the interpretation of
+     existing doc strings. PHP-Parser will now use the new interpretation.
+   * Flexible heredoc/nowdoc strings require special support from the lexer. Because this is not
+     available on PHP versions before 7.3, support has to be emulated. This emulation is not perfect
+     and some cases which we do not expect to occur in practice (such as flexible doc strings being
+     nested within each other through abuse of variable-variable interpolation syntax) may not be
+     recognized correctly.
 
 Version 4.0.4 (2018-09-18)
 --------------------------
diff --git a/README.md b/README.md
index 5fea5c9..5ae789f 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ PHP Parser
 This is a PHP 5.2 to PHP 7.2 parser written in PHP. Its purpose is to simplify static code analysis and
 manipulation.
 
-[**Documentation for version 4.x**][doc_master] (stable; for running on PHP >= 7.0; for parsing PHP 5.2 to PHP 7.2).
+[**Documentation for version 4.x**][doc_master] (stable; for running on PHP >= 7.0; for parsing PHP 5.2 to PHP 7.3).
 
 [Documentation for version 3.x][doc_3_x] (unsupported; for running on PHP >= 5.5; for parsing PHP 5.2 to PHP 7.2).
 
diff --git a/composer.json b/composer.json
index 7ae425f..12e8458 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
     "bin": ["bin/php-parse"],
     "extra": {
         "branch-alias": {
-            "dev-master": "4.0-dev"
+            "dev-master": "4.1-dev"
         }
     }
 }