diff --git a/package-lock.json b/package-lock.json
index 6b8d968..da473e0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
 	"name": "fenfurnace",
-	"version": "0.3.1",
+	"version": "0.4.0",
 	"lockfileVersion": 1,
 	"requires": true,
 	"dependencies": {
diff --git a/package.json b/package.json
index 14c6025..94fbdba 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "fenfurnace",
-	"version": "0.3.1-next",
+	"version": "0.4.0",
 	"description": "A chess engine designed to work entirely from a FEN position.",
 	"keywords": [
 		"chess",
diff --git a/readme.md b/readme.md
index 5f5037b..955eaf3 100644
--- a/readme.md
+++ b/readme.md
@@ -44,13 +44,13 @@ FenFurnace is available [on npm](https://www.npmjs.org/package/fenfurnace):
 The following values are given in import `gameData`:
 - `castling`: `{ w: { k, q }, b: { k, q } }` (each boolean)
 - `boardArray` (array)
-- `enpassantSquare` (cell string or `-`)
+- `enpassantSquare` (string or `-`)
 - `moveList` (array)
 - `logList` (array)
 - `currentTurn` (`null` or `w` or `b`)
 - `halfMoveCount` (int)
 - `moveNumber` (int)
-- `promotionPiece` (pieceId string)
+- `promotionPiece` (char)
 
 ## Build