diff --git a/core/includes/common.inc b/core/includes/common.inc
index 7a97da31902283e4d52368a4d3fc5c98bf924de7..1cf53b647a5e86c3f9a3c17d949280a4678c65b2 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1371,12 +1371,15 @@ function filter_xss($string, $allowed_tags = array('a', 'em', 'strong', 'cite',
  * @see filter_xss()
  */
 function partial_decode_entities_safe($string) {
-  // Decimal numeric entities.
-  $string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
-  // Hexadecimal numeric entities.
-  $string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
-  // Named entities.
-  $string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
+  // Do nothing if there are no '&' characters in $string.
+  if(strpos($string, '&') !== FALSE) {
+    // Decimal numeric entities.
+    $string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
+    // Hexadecimal numeric entities.
+    $string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);
+    // Named entities.
+    $string = preg_replace('/&([A-Za-z][A-Za-z0-9]*;)/', '&\1', $string);
+  }
   return $string;
 }
 
diff --git a/core/lib/Drupal/Core/Template/AttributeString.php b/core/lib/Drupal/Core/Template/AttributeString.php
index 9c953bd450ee06a9fa51f1eef90c631ba82fcf0d..87ab6bd7c13e550324c045915d294e5df1e6082a 100644
--- a/core/lib/Drupal/Core/Template/AttributeString.php
+++ b/core/lib/Drupal/Core/Template/AttributeString.php
@@ -31,11 +31,9 @@ public function __toString() {
     $this->printed = TRUE;
     $string = check_plain($this->value);
 
-    // Decode legal HTML entities on our security whitelist that may have been
-    // inappropriately sanitized by check_plain().
-    if(strpos($string, '&') !== FALSE) {
-      $string = partial_decode_entities_safe($string);
-    }
+    // Allow well-formed HTML entities on our security whitelist.
+    $string = partial_decode_entities_safe($string);
+
     return $string;
   }
 
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/AttributesUnitTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/AttributesUnitTest.php
index 77a0e6b5700e397be2f6fd2f3ccc8c8a91cfdab4..0e51b1ebf931529afe7e4ee8c256d44b0ad088b2 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/AttributesUnitTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/AttributesUnitTest.php
@@ -47,6 +47,9 @@ function testDrupalAttributes() {
     // Verify that HTML encoded named characters are preserved.
     $this->assertIdentical((string) new Attribute(array('title' => '®')), ' title="®"', 'HTML Encoded named character entity attribute values are preserved.');
 
+    // Verify that iconic Unicode characters are preserved.
+    $this->assertIdentical((string) new Attribute(array('title' => '©')), ' title="©"', 'Iconic Unicode character attribute values are preserved.');
+
     // Verify multi-value attributes are concatenated with spaces.
     $attributes = array('class' => array('first', 'last'));
     $this->assertIdentical((string) new Attribute(array('class' => array('first', 'last'))), ' class="first last"', 'Concatenate multi-value attributes.');