diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8b9808aae..364ba041d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@
 * Produce a better error message for a nested property whose name starts with
   `--`.
 
+* Fix a crash when a selector ends in an escaped backslash.
+
 ## 1.57.1
 
 * No user-visible changes.
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index 295f753db..21ae174a5 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -114,7 +114,7 @@ int? _lastNonWhitespace(String string, {bool excludeEscape = false}) {
     if (!isWhitespace(codeUnit)) {
       if (excludeEscape &&
           i != 0 &&
-          i != string.length &&
+          i != string.length - 1 &&
           codeUnit == $backslash) {
         return i + 1;
       } else {