diff --git a/CHANGELOG.md b/CHANGELOG.md
index f829f18e2..930ba70b0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 1.17.1
+
+* Properly quote attribute selector values that start with identifiers but end
+  with a non-identifier character.
+
 ## 1.17.0
 
 * Improve error output, particularly for errors that cover multiple lines.
diff --git a/lib/src/parse/parser.dart b/lib/src/parse/parser.dart
index e6fe5618c..baaabc771 100644
--- a/lib/src/parse/parser.dart
+++ b/lib/src/parse/parser.dart
@@ -31,6 +31,16 @@ class Parser {
   static String parseIdentifier(String text, {Logger logger}) =>
       Parser(text, logger: logger)._parseIdentifier();
 
+  /// Returns whether [text] is a valid CSS identifier.
+  static bool isIdentifier(String text, {Logger logger}) {
+    try {
+      parseIdentifier(text, logger: logger);
+      return true;
+    } on SassFormatException {
+      return false;
+    }
+  }
+
   @protected
   Parser(String contents, {url, Logger logger})
       : scanner = SpanScanner(contents, sourceUrl: url),
diff --git a/lib/src/visitor/serialize.dart b/lib/src/visitor/serialize.dart
index 96c6ac1a4..037582908 100644
--- a/lib/src/visitor/serialize.dart
+++ b/lib/src/visitor/serialize.dart
@@ -15,6 +15,7 @@ import '../ast/node.dart';
 import '../ast/selector.dart';
 import '../color_names.dart';
 import '../exception.dart';
+import '../parse/parser.dart';
 import '../utils.dart';
 import '../util/character.dart';
 import '../util/no_source_map_buffer.dart';
@@ -903,7 +904,10 @@ class _SerializeVisitor implements CssVisitor, ValueVisitor, SelectorVisitor {
     _buffer.write(attribute.name);
     if (attribute.op != null) {
       _buffer.write(attribute.op);
-      if (_isIdentifier(attribute.value)) {
+      if (Parser.isIdentifier(attribute.value) &&
+          // Emit identifiers that start with `--` with quotes, because IE11
+          // doesn't consider them to be valid identifiers.
+          !attribute.value.startsWith('--')) {
         _buffer.write(attribute.value);
       } else {
         _visitQuotedString(attribute.value);
@@ -1133,64 +1137,6 @@ class _SerializeVisitor implements CssVisitor, ValueVisitor, SelectorVisitor {
       return false;
     }
   }
-
-  /// Returns whether [text] is a valid identifier.
-  ///
-  /// This *doesn't* consider identifiers beginning with `--` to be valid,
-  /// because IE 11 doesn't.
-  bool _isIdentifier(String text) {
-    var scanner = StringScanner(text);
-    scanner.scanChar($dash);
-
-    if (scanner.isDone) return false;
-    var first = scanner.readChar();
-
-    if (isNameStart(first)) {
-      if (scanner.isDone) return true;
-      scanner.readChar();
-    } else if (first == $backslash) {
-      if (!_consumeEscape(scanner)) return false;
-    } else {
-      return false;
-    }
-
-    while (true) {
-      var next = scanner.peekChar();
-      if (next == null) return true;
-
-      if (isName(next)) {
-        scanner.readChar();
-      } else if (next == $backslash) {
-        if (!_consumeEscape(scanner)) return false;
-      } else {
-        return false;
-      }
-    }
-  }
-
-  /// Consumes an escape sequence in [scanner].
-  ///
-  /// Returns whether a valid escape was consumed.
-  bool _consumeEscape(StringScanner scanner) {
-    scanner.expectChar($backslash);
-
-    var first = scanner.peekChar();
-    if (first == null || isNewline(first)) return false;
-
-    if (isHex(first)) {
-      for (var i = 0; i < 6; i++) {
-        var next = scanner.peekChar();
-        if (next == null || !isHex(next)) break;
-        scanner.readChar();
-      }
-      if (isWhitespace(scanner.peekChar())) scanner.readChar();
-    } else {
-      if (scanner.isDone) return false;
-      scanner.readChar();
-    }
-
-    return true;
-  }
 }
 
 /// An enum of generated CSS styles.
diff --git a/pubspec.yaml b/pubspec.yaml
index 2bd3bcb6c..916d2db67 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sass
-version: 1.17.0
+version: 1.17.1
 description: A Sass implementation in Dart.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/sass/dart-sass