diff --git a/core/lib/Drupal/Core/Asset/CssOptimizer.php b/core/lib/Drupal/Core/Asset/CssOptimizer.php
index 1a3cb90..e573d85 100644
--- a/core/lib/Drupal/Core/Asset/CssOptimizer.php
+++ b/core/lib/Drupal/Core/Asset/CssOptimizer.php
@@ -217,7 +217,7 @@ protected function processCss($contents, $optimize = FALSE) {
         # - Colon: Retain :pseudo-selectors.
         | ([\(:])\s+
       >xS',
-        // Only one of the three capturing groups will match, so its reference
+        // Only one of the four capturing groups will match, so its reference
         // will contain the wanted value and the references for the
         // two non-matching groups will be replaced with empty strings.
         '$1$2$3$4',
diff --git a/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css b/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css
index a823346..3363497 100644
--- a/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css
+++ b/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css
@@ -19,6 +19,22 @@ img[style*='float: left'] {
     padding-right:5px;
 }
 
+li.node-readmore a:after {
+  content: ": a word, and a phrase, etc.";
+}
+
+li.node-readmore a:after {
+  content: ': a word, and a phrase, etc.';
+}
+
+li.node-readmore a:after {
+  content: " (a word - and a phrase)";
+}
+
+li.node-readmore a:after {
+  content: ' (a word - and a phrase)';
+}
+
 /* A multiline IE-mac hack (v.2) taken from Zen theme*/
 /* Hides from IE-mac \*/
 html .clear-block {
diff --git a/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css.optimized.css b/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css.optimized.css
index 1c8afbf..b3a2833 100644
--- a/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css.optimized.css
+++ b/core/tests/Drupal/Tests/Core/Asset/css_test_files/comment_hacks.css.optimized.css
@@ -1 +1 @@
-.test1{display:block;}img[style*="float: right"]{padding-left:5px;}img[style*='float: left']{padding-right:5px;}html .clear-block{height:1%;}.clear-block{display:block;font:italic bold 12px/30px Georgia,serif;}.test2{display:block;}.bkslshv1{background-color:#c00;}.test3{display:block;}.test4{display:block;}.comment-in-double-quotes:before{content:"/* ";}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-double-quotes:after{content:" */";}.comment-in-single-quotes:before{content:'/*';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-single-quotes:after{content:'*/';}.comment-in-mixed-quotes:before{content:'"/*"';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-mixed-quotes:after{content:"'*/'";}.comment-in-quotes-with-escaped:before{content:'/* \" \' */';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-quotes-with-escaped:after{content:"*/ \" \ '";}
+.test1{display:block;}img[style*="float: right"]{padding-left:5px;}img[style*='float: left']{padding-right:5px;}li.node-readmore a:after{content:": a word, and a phrase, etc.";}li.node-readmore a:after{content:': a word, and a phrase, etc.';}li.node-readmore a:after{content:" (a word - and a phrase)";}li.node-readmore a:after{content:' (a word - and a phrase)';}html .clear-block{height:1%;}.clear-block{display:block;font:italic bold 12px/30px Georgia,serif;}.test2{display:block;}.bkslshv1{background-color:#c00;}.test3{display:block;}.test4{display:block;}.comment-in-double-quotes:before{content:"/* ";}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-double-quotes:after{content:" */";}.comment-in-single-quotes:before{content:'/*';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-single-quotes:after{content:'*/';}.comment-in-mixed-quotes:before{content:'"/*"';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-mixed-quotes:after{content:"'*/'";}.comment-in-quotes-with-escaped:before{content:'/* \" \' */';}.this_rule_must_stay{color:#f00;background-color:#fff;}.comment-in-quotes-with-escaped:after{content:"*/ \" \ '";}