diff --git a/package-lock.json b/package-lock.json
index 03cd95a..3e95046 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
 	"name": "fenfurnace",
-	"version": "0.2.4",
+	"version": "0.2.5",
 	"lockfileVersion": 2,
 	"requires": true,
 	"packages": {
 		"": {
 			"name": "fenfurnace",
-			"version": "0.2.4",
+			"version": "0.2.5",
 			"license": "ISC",
 			"devDependencies": {
 				"html-webpack-plugin": "^5.3.1",
diff --git a/package.json b/package.json
index 4642428..0fa29d9 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "fenfurnace",
-	"version": "0.2.4",
+	"version": "0.2.5",
 	"description": "A chess engine designed to work entirely from a FEN position.",
 	"keywords": [
 		"chess",
diff --git a/src/validation.js b/src/validation.js
index 8eaa763..14e3b29 100644
--- a/src/validation.js
+++ b/src/validation.js
@@ -183,10 +183,10 @@ export function makeMove(startCell, endCell, { isTest } = {}) {
 	}
 
 	//if rook or king make castling invalid
-	if (piece === 'k') {
+	if (piece.toLowerCase() === 'k') {
 		global.castling[colour] = { k: false, q: false };
-	} else if (piece === 'r') {
-		const isKingside = startCell === 'H';
+	} else if (piece.toLowerCase() === 'r') {
+		const isKingside = startCell[0] === 'H';
 		const side = isKingside ? 'k' : 'q';
 		global.castling[colour][side] = false;
 	}