diff --git a/lib/src/parse/stylesheet.dart b/lib/src/parse/stylesheet.dart
index 19d2d6929..165b3bec6 100644
--- a/lib/src/parse/stylesheet.dart
+++ b/lib/src/parse/stylesheet.dart
@@ -2905,7 +2905,10 @@ abstract class StylesheetParser extends Parser {
           brackets.add(opposite(bracket));
 
         case $rparen || $rbracket:
-          if (brackets.isEmpty) break loop;
+          if (brackets.isEmpty) {
+            scanner.error(
+                'Unexpected "${String.fromCharCode(scanner.peekChar()!)}".');
+          }
           var bracket = brackets.removeLast();
           scanner.expectChar(bracket);
           buffer.writeCharCode(bracket);