diff --git a/dev/src/ExpressionLexer.js b/dev/src/ExpressionLexer.js
index 4e80fef8..e848d29e 100644
--- a/dev/src/ExpressionLexer.js
+++ b/dev/src/ExpressionLexer.js
@@ -475,7 +475,7 @@ export default class ExpressionLexer {
 		// Note: Chrome does weird things with \x & \u depending on a number of factors, we ignore this.
 		let i = token.i, match, profile = this._profile;
 		let sub = str.substr(i + 1), c = sub[0], val;
-		if (i + 1 === (closeIndex || str.length)) {
+		if (closeIndex === i + 1 || str.length === i + 1) {
 			token.error = {id: "esccharopen"};
 			return;
 		}
@@ -722,4 +722,4 @@ ExpressionLexer.ANCHOR_TYPES = {
 	"wordboundary": true,
 	"notwordboundary": true,
 	"prevmatchend": true
-}
\ No newline at end of file
+}