diff --git a/acorn/CHANGELOG.md b/acorn/CHANGELOG.md
index 6b71c9899..1438da677 100644
--- a/acorn/CHANGELOG.md
+++ b/acorn/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 6.4.0 (2019-11-26)
+
+### New features
+
+Add a static `acorn` property to the `Parser` class that contains the entire module interface, to allow plugins to access the instance of the library that they are acting on.
+
 ## 6.3.0 (2019-08-12)
 
 ### New features
diff --git a/acorn/package.json b/acorn/package.json
index 480ea2d25..f862c38b6 100644
--- a/acorn/package.json
+++ b/acorn/package.json
@@ -4,7 +4,7 @@
   "homepage": "https://github.com/acornjs/acorn",
   "main": "dist/acorn.js",
   "module": "dist/acorn.mjs",
-  "version": "6.3.0",
+  "version": "6.4.0",
   "engines": {"node": ">=0.4.0"},
   "maintainers": [
     {
diff --git a/acorn/src/index.js b/acorn/src/index.js
index 0834c9db1..506a989dd 100644
--- a/acorn/src/index.js
+++ b/acorn/src/index.js
@@ -31,7 +31,7 @@ import {isIdentifierChar, isIdentifierStart} from "./identifier"
 import {Token} from "./tokenize"
 import {isNewLine, lineBreak, lineBreakG, nonASCIIwhitespace} from "./whitespace"
 
-export const version = "6.3.0"
+export const version = "6.4.0"
 export {
   Parser,
   defaultOptions,