diff --git a/includes/sanitizers/class-amp-style-sanitizer.php b/includes/sanitizers/class-amp-style-sanitizer.php
index 961ead0b663..f99ad2bceb2 100644
--- a/includes/sanitizers/class-amp-style-sanitizer.php
+++ b/includes/sanitizers/class-amp-style-sanitizer.php
@@ -133,6 +133,14 @@ class AMP_Style_Sanitizer extends AMP_Base_Sanitizer {
 	 */
 	private $used_class_names = array();
 
+	/**
+	 * Tag names used in document.
+	 *
+	 * @since 1.0
+	 * @var array
+	 */
+	private $used_tag_names = array();
+
 	/**
 	 * XPath.
 	 *
@@ -245,6 +253,24 @@ private function get_used_class_names() {
 		return $this->used_class_names;
 	}
 
+
+	/**
+	 * Get list of all the tag names used in the document.
+	 *
+	 * @since 1.0
+	 * @return array Used tag names.
+	 */
+	private function get_used_tag_names() {
+		if ( empty( $this->used_tag_names ) ) {
+			$used_tag_names = array();
+			foreach ( $this->dom->getElementsByTagName( '*' ) as $el ) {
+				$used_tag_names[ $el->tagName ] = true;
+			}
+			$this->used_tag_names = array_keys( $used_tag_names );
+		}
+		return $this->used_tag_names;
+	}
+
 	/**
 	 * Sanitize CSS styles within the HTML contained in this instance's DOMDocument.
 	 *
@@ -531,7 +557,7 @@ private function process_stylesheet( $stylesheet, $node, $options = array() ) {
 
 		$cache_key = md5( $stylesheet . serialize( $cache_impacting_options ) ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.serialize_serialize
 
-		$cache_group = 'amp-parsed-stylesheet-v2';
+		$cache_group = 'amp-parsed-stylesheet-v4';
 		if ( wp_using_ext_object_cache() ) {
 			$parsed = wp_cache_get( $cache_key, $cache_group );
 		} else {
@@ -614,6 +640,7 @@ function ( $value ) {
 			$validation_errors = $this->process_css_list( $css_document, $options );
 
 			$output_format = Sabberworm\CSS\OutputFormat::createCompact();
+			$output_format->setSemicolonAfterLastRule( false );
 
 			$before_declaration_block          = '/*AMP_WP_BEFORE_DECLARATION_BLOCK*/';
 			$between_selectors                 = '/*AMP_WP_BETWEEN_SELECTORS*/';
@@ -644,18 +671,34 @@ function ( $value ) {
 
 					$selectors_parsed = array();
 					foreach ( $selectors as $selector ) {
-						$classes = array();
+						$selectors_parsed[ $selector ] = array();
 
-						// Remove :not() to eliminate false negatives, such as with `body:not(.title-tagline-hidden) .site-branding-text`.
-						$reduced_selector = preg_replace( '/:not\(.+?\)/', '', $selector );
+						// Remove :not() and pseudo selectors to eliminate false negatives, such as with `body:not(.title-tagline-hidden) .site-branding-text`.
+						$reduced_selector = preg_replace( '/:[a-zA-Z0-9_-]+(\(.+?\))?/', '', $selector );
 
 						// Remove attribute selectors to eliminate false negative, such as with `.social-navigation a[href*="example.com"]:before`.
 						$reduced_selector = preg_replace( '/\[\w.*?\]/', '', $reduced_selector );
 
-						if ( preg_match_all( '/(?<=\.)([a-zA-Z0-9_-]+)/', $reduced_selector, $matches ) ) {
-							$classes = $matches[0];
+						$reduced_selector = preg_replace_callback(
+							'/\.([a-zA-Z0-9_-]+)/',
+							function( $matches ) use ( $selector, &$selectors_parsed ) {
+								$selectors_parsed[ $selector ]['classes'][] = $matches[1];
+								return '';
+							},
+							$reduced_selector
+						);
+						$reduced_selector = preg_replace_callback(
+							'/#([a-zA-Z0-9_-]+)/',
+							function( $matches ) use ( $selector, &$selectors_parsed ) {
+								$selectors_parsed[ $selector ]['ids'][] = $matches[1];
+								return '';
+							},
+							$reduced_selector
+						);
+
+						if ( preg_match_all( '/[a-zA-Z0-9_-]+/', $reduced_selector, $matches ) ) {
+							$selectors_parsed[ $selector ]['tags'] = $matches[0];
 						}
-						$selectors_parsed[ $selector ] = $classes;
 					}
 
 					// Restore calc() functions that were replaced with placeholders.
@@ -1403,6 +1446,7 @@ function( $selector ) {
 		$stylesheet_set['processed_nodes'] = array();
 
 		$final_size = 0;
+		$dom        = $this->dom;
 		foreach ( $stylesheet_set['pending_stylesheets'] as &$pending_stylesheet ) {
 			$stylesheet = '';
 			foreach ( $pending_stylesheet['stylesheet'] as $stylesheet_part ) {
@@ -1412,12 +1456,34 @@ function( $selector ) {
 					list( $selectors_parsed, $declaration_block ) = $stylesheet_part;
 					if ( $should_tree_shake ) {
 						$selectors = array();
-						foreach ( $selectors_parsed as $selector => $class_names ) {
+						foreach ( $selectors_parsed as $selector => $parsed_selector ) {
 							$should_include = (
 								( $dynamic_selector_pattern && preg_match( $dynamic_selector_pattern, $selector ) )
 								||
-								// If all class names are used in the doc.
-								0 === count( array_diff( $class_names, $this->get_used_class_names() ) )
+								(
+									// If all class names are used in the doc.
+									(
+										empty( $parsed_selector['classes'] )
+										||
+										0 === count( array_diff( $parsed_selector['classes'], $this->get_used_class_names() ) )
+									)
+									&&
+									// If all IDs are used in the doc.
+									(
+										empty( $parsed_selector['ids'] )
+										||
+										0 === count( array_filter( $parsed_selector['ids'], function( $id ) use ( $dom ) {
+											return ! $dom->getElementById( $id );
+										} ) )
+									)
+									&&
+									// If tag names are present in the doc.
+									(
+										empty( $parsed_selector['tags'] )
+										||
+										0 === count( array_diff( $parsed_selector['tags'], $this->get_used_tag_names() ) )
+									)
+								)
 							);
 							if ( $should_include ) {
 								$selectors[] = $selector;
diff --git a/tests/test-amp-style-sanitizer.php b/tests/test-amp-style-sanitizer.php
index d5f82cd0d5e..7726fba5a8d 100644
--- a/tests/test-amp-style-sanitizer.php
+++ b/tests/test-amp-style-sanitizer.php
@@ -29,7 +29,7 @@ public function get_body_style_attribute_data() {
 				'<span style="color: #00ff00;">This is green.</span>',
 				'<span class="amp-wp-bb01159">This is green.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-bb01159{color:#0f0;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-bb01159{color:#0f0}',
 				),
 			),
 
@@ -37,7 +37,7 @@ public function get_body_style_attribute_data() {
 				'<span style="color  :   #00ff00">This is green.</span>',
 				'<span class="amp-wp-0837823">This is green.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-0837823{color:#0f0;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-0837823{color:#0f0}',
 				),
 			),
 
@@ -45,7 +45,7 @@ public function get_body_style_attribute_data() {
 				'<span style="color: #00ff00; background-color: #000; ">This is green.</span>',
 				'<span class="amp-wp-c71affe">This is green.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-c71affe{color:#0f0;background-color:#000;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-c71affe{color:#0f0;background-color:#000}',
 				),
 			),
 
@@ -53,7 +53,7 @@ public function get_body_style_attribute_data() {
 				'<span style="display: none;">Kses-banned properties are allowed since Kses will have already applied if user does not have unfiltered_html.</span>',
 				'<span class="amp-wp-224b51a">Kses-banned properties are allowed since Kses will have already applied if user does not have unfiltered_html.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-224b51a{display:none;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-224b51a{display:none}',
 				),
 			),
 
@@ -61,7 +61,7 @@ public function get_body_style_attribute_data() {
 				'<span style="padding:1px; margin: 2px !important; outline: 3px;">!important is converted.</span>',
 				'<span class="amp-wp-6a75598">!important is converted.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-6a75598{padding:1px;outline:3px;}:root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-6a75598{margin:2px;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-6a75598{padding:1px;outline:3px}:root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-6a75598{margin:2px}',
 				),
 			),
 
@@ -69,7 +69,7 @@ public function get_body_style_attribute_data() {
 				'<span style="color: red  !  important;">!important is converted.</span>',
 				'<span class="amp-wp-952600b">!important is converted.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-952600b{color:red;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-952600b{color:red}',
 				),
 			),
 
@@ -77,7 +77,7 @@ public function get_body_style_attribute_data() {
 				'<span style="color: red !important; background: blue!important;">!important is converted.</span>',
 				'<span class="amp-wp-1e2bfaa">!important is converted.</span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-1e2bfaa{color:red;background:blue;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-1e2bfaa{color:red;background:blue}',
 				),
 			),
 
@@ -85,8 +85,8 @@ public function get_body_style_attribute_data() {
 				'<span style="color: #00ff00;"><span style="color: #ff0000;">This is red.</span></span>',
 				'<span class="amp-wp-bb01159"><span class="amp-wp-cc68ddc">This is red.</span></span>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-bb01159{color:#0f0;}',
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cc68ddc{color:#f00;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-bb01159{color:#0f0}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cc68ddc{color:#f00}',
 				),
 			),
 
@@ -94,7 +94,7 @@ public function get_body_style_attribute_data() {
 				'<figure class="alignleft" style="background: #000"></figure>',
 				'<figure class="alignleft amp-wp-2864855"></figure>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-2864855{background:#000;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-2864855{background:#000}',
 				),
 			),
 
@@ -102,7 +102,7 @@ public function get_body_style_attribute_data() {
 				'<style>div > span { font-weight:bold !important; font-style: italic; } @media screen and ( max-width: 640px ) { div > span { font-weight:normal !important; font-style: normal; } }</style><div><span>bold!</span></div>',
 				'<div><span>bold!</span></div>',
 				array(
-					'div > span{font-style:italic;}@media screen and ( max-width: 640px ){div > span{font-style:normal;}:root:not(#_):not(#_) div > span{font-weight:normal;}}:root:not(#_):not(#_) div > span{font-weight:bold;}',
+					'div > span{font-style:italic}@media screen and ( max-width: 640px ){div > span{font-style:normal}:root:not(#_):not(#_) div > span{font-weight:normal}}:root:not(#_):not(#_) div > span{font-weight:bold}',
 				),
 			),
 
@@ -110,7 +110,7 @@ public function get_body_style_attribute_data() {
 				'<style>button { behavior: url(hilite.htc) /* IE only */; font-weight:bold; -moz-binding: url(http://www.example.org/xbl/htmlBindings.xml#checkbox); /*XBL*/ } @media screen { button { behavior: url(hilite.htc) /* IE only */; font-weight:bold; -moz-binding: url(http://www.example.org/xbl/htmlBindings.xml#checkbox); /*XBL*/ } }</style><button>Click</button>',
 				'<button>Click</button>',
 				array(
-					'button{font-weight:bold;}@media screen{button{font-weight:bold;}}',
+					'button{font-weight:bold}@media screen{button{font-weight:bold}}',
 				),
 				array( 'illegal_css_property', 'illegal_css_property', 'illegal_css_property', 'illegal_css_property' ),
 			),
@@ -126,7 +126,7 @@ public function get_body_style_attribute_data() {
 				'<style>@charset "utf-8"; @namespace svg url(http://www.w3.org/2000/svg); @page { margin: 1cm; } @viewport { width: device-width; } @counter-style thumbs { system: cyclic; symbols: "\1F44D"; suffix: " "; } body { color: black; }</style>',
 				'',
 				array(
-					'body{color:black;}',
+					'body{color:black}',
 				),
 				array( 'illegal_css_at_rule', 'illegal_css_at_rule', 'illegal_css_at_rule', 'illegal_css_at_rule', 'illegal_css_at_rule' ),
 			),
@@ -135,17 +135,17 @@ public function get_body_style_attribute_data() {
 				'<style>@media screen and ( max-width: 640px ) { body { font-size: small; } } @font-face { font-family: "Open Sans"; src: url("/fonts/OpenSans-Regular-webfont.woff2") format("woff2"); } @supports (display: grid) { div { display: grid; } } @-moz-keyframes appear { from { opacity: 0.0; } to { opacity: 1.0; } } @keyframes appear { from { opacity: 0.0; } to { opacity: 1.0; } }</style>',
 				'',
 				array(
-					'@media screen and ( max-width: 640px ){body{font-size:small;}}@font-face{font-family:"Open Sans";src:url("/fonts/OpenSans-Regular-webfont.woff2") format("woff2");}@supports (display: grid){div{display:grid;}}@-moz-keyframes appear{from{opacity:0;}to{opacity:1;}}@keyframes appear{from{opacity:0;}to{opacity:1;}}',
+					'@media screen and ( max-width: 640px ){body{font-size:small}}@font-face{font-family:"Open Sans";src:url("/fonts/OpenSans-Regular-webfont.woff2") format("woff2")}@supports (display: grid){div{display:grid}}@-moz-keyframes appear{from{opacity:0}to{opacity:1}}@keyframes appear{from{opacity:0}to{opacity:1}}',
 				),
 			),
 
 			'selector_specificity' => array(
-				'<style>#child {color:red !important;} #parent #child {color:pink !important;} .foo { color:blue !important; } #me .foo { color: green !important; }</style><div id="parent"><span id="child" class="foo bar baz">one</span><span style="color: yellow;">two</span><span style="color: purple !important;">three</span></div>',
+				'<style>#child {color:red !important} #parent #child {color:pink !important} .foo { color:blue !important; } #me .foo { color: green !important; }</style><div id="parent"><span id="child" class="foo bar baz">one</span><span style="color: yellow;">two</span><span style="color: purple !important;">three</span></div>',
 				'<div id="parent"><span id="child" class="foo bar baz">one</span><span class="amp-wp-64b4fd4">two</span><span class="amp-wp-ab79d9e">three</span></div>',
 				array(
-					':root:not(#_) #child{color:red;}:root:not(#_):not(#_) #parent #child{color:pink;}:root:not(#_) .foo{color:blue;}:root:not(#_):not(#_) #me .foo{color:green;}',
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-64b4fd4{color:yellow;}',
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-ab79d9e{color:purple;}',
+					':root:not(#_) #child{color:red}:root:not(#_):not(#_) #parent #child{color:pink}:root:not(#_) .foo{color:blue}:root:not(#_):not(#_) #me .foo{color:green}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-64b4fd4{color:yellow}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-ab79d9e{color:purple}',
 				),
 			),
 
@@ -153,7 +153,7 @@ public function get_body_style_attribute_data() {
 				'<table><colgroup><col width="253"/></colgroup></table>',
 				'<table><colgroup><col class="amp-wp-cbcb5c2"></colgroup></table>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cbcb5c2{width:253px;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cbcb5c2{width:253px}',
 				),
 			),
 
@@ -161,7 +161,7 @@ public function get_body_style_attribute_data() {
 				'<table><colgroup><col width="50%"/></colgroup></table>',
 				'<table><colgroup><col class="amp-wp-cd7753e"></colgroup></table>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cd7753e{width:50%;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-cd7753e{width:50%}',
 				),
 			),
 
@@ -175,7 +175,7 @@ public function get_body_style_attribute_data() {
 				'<table><colgroup><col width="50" style="background-color: red; width: 60px"/></colgroup></table>',
 				'<table><colgroup><col class="amp-wp-c8aa9e9"></colgroup></table>',
 				array(
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-c8aa9e9{width:50px;width:60px;background-color:red;}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-c8aa9e9{width:50px;width:60px;background-color:red}',
 				),
 			),
 		);
@@ -222,12 +222,12 @@ public function test_body_style_attribute_sanitizer( $source, $expected_content,
 	public function get_link_and_style_test_data() {
 		return array(
 			'multiple_amp_custom_and_other_styles' => array(
-				'<html amp><head><meta charset="utf-8"><style amp-custom>b {color:red !important}</style><style amp-custom>i {color:blue}</style><style type="text/css">u {color:green; text-decoration: underline !important;}</style></head><body><style>s {color:yellow} /* So !important! */</style></body></html>',
+				'<html amp><head><meta charset="utf-8"><style amp-custom>b {color:red !important}</style><style amp-custom>i {color:blue}</style><style type="text/css">u {color:green; text-decoration: underline !important}</style></head><body><style>s {color:yellow} /* So !important! */</style><b>1</b><i>i</i><u>u</u><s>s</s></body></html>',
 				array(
-					':root:not(#_):not(#_) b{color:red;}',
-					'i{color:blue;}',
-					'u{color:green;}:root:not(#_):not(#_) u{text-decoration:underline;}',
-					's{color:yellow;}',
+					':root:not(#_):not(#_) b{color:red}',
+					'i{color:blue}',
+					'u{color:green}:root:not(#_):not(#_) u{text-decoration:underline}',
+					's{color:yellow}',
 				),
 				array(),
 			),
@@ -240,36 +240,36 @@ public function get_link_and_style_test_data() {
 					'strong.before-dashicon',
 					'.dashicons-dashboard:before',
 					'strong.after-dashicon',
-					':root:not(#_):not(#_) s{color:yellow;}',
+					':root:not(#_):not(#_) s{color:yellow}',
 				),
 				array(),
 			),
 			'style_with_no_head' => array(
-				'<html amp><body>Not good!<style>body{color:red;}</style></body></html>',
+				'<html amp><body>Not good!<style>body{color:red}</style></body></html>',
 				array(
-					'body{color:red;}',
+					'body{color:red}',
 				),
 				array(),
 			),
 			'style_with_not_selectors' => array(
 				'<html amp><head><meta charset="utf-8"><style amp-custom>body.bar > p:not(.baz) { color:red; } body.foo:not(.bar) > p { color:blue; } body.foo:not(.bar) p:not(.baz) { color:green; } body.foo p { color:yellow; }</style></head><body class="foo"><p>Hello</p></body></html>',
 				array(
-					'body.foo:not(.bar) > p{color:blue;}body.foo:not(.bar) p:not(.baz){color:green;}body.foo p{color:yellow;}',
+					'body.foo:not(.bar) > p{color:blue}body.foo:not(.bar) p:not(.baz){color:green}body.foo p{color:yellow}',
 				),
 				array(),
 			),
 			'style_with_attribute_selectors' => array(
 				'<html amp><head><meta charset="utf-8"><style amp-custom>.social-navigation a[href*="example.com"] { color:red; } .social-navigation a.examplecom { color:blue; }</style></head><body class="foo"><nav class="social-navigation"><a href="https://example.com/">Example</a></nav></body></html>',
 				array(
-					'.social-navigation a[href*="example.com"]{color:red;}',
+					'.social-navigation a[href*="example.com"]{color:red}',
 				),
 				array(),
 			),
 			'style_on_root_element' => array(
 				'<html amp style="color:red;"><head><meta charset="utf-8"><style amp-custom>html { background-color: blue !important; }</style></head><body>Hi</body></html>',
 				array(
-					'html:not(#_):not(#_){background-color:blue;}',
-					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-10b06ba{color:red;}',
+					'html:not(#_):not(#_){background-color:blue}',
+					':root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-10b06ba{color:red}',
 				),
 				array(),
 			),
@@ -286,9 +286,9 @@ public function get_link_and_style_test_data() {
 					'</body></html>',
 				) ),
 				array(
-					'form [submit-success] b,div[submit-failure] b{color:green;}',
-					'amp-live-list li .highlighted{background:yellow;}',
-					'body amp-list .portland{color:blue;}',
+					'form [submit-success] b,div[submit-failure] b{color:green}',
+					'amp-live-list li .highlighted{background:yellow}',
+					'body amp-list .portland{color:blue}',
 				),
 				array(),
 			),
@@ -297,13 +297,13 @@ public function get_link_and_style_test_data() {
 					'<html amp><head>',
 					'<style amp-custom>body { color: red; width: -webkit-calc( 1px + 2vh * 3pt - ( 4em / 5 ) ); outline: solid 1px blue; }</style>',
 					'<style amp-custom>.alignwide{ max-width: calc(50% + 22.5rem); border: solid 1px red; }</style>',
-					'<style amp-custom>.alignwide{ height: calc(10% + ( 1px ); color: red; content: ")";}</style>', // Test unbalanced parentheses.
+					'<style amp-custom>.alignwide{ height: calc(10% + ( 1px ); color: red; content: ")"}</style>', // Test unbalanced parentheses.
 					'</head><body><div class="alignwide"></div></body></html>',
 				) ),
 				array(
-					'body{color:red;width:-webkit-calc( 1px + 2vh * 3pt - ( 4em / 5 ) );outline:solid 1px blue;}',
-					'.alignwide{max-width:calc(50% + 22.5rem);border:solid 1px red;}',
-					'.alignwide{color:red;content:")";}',
+					'body{color:red;width:-webkit-calc( 1px + 2vh * 3pt - ( 4em / 5 ) );outline:solid 1px blue}',
+					'.alignwide{max-width:calc(50% + 22.5rem);border:solid 1px red}',
+					'.alignwide{color:red;content:")"}',
 				),
 				array(),
 			),
@@ -448,10 +448,10 @@ public function test_class_amp_bind_preservation() {
 		$sanitizer->sanitize();
 		$this->assertEquals( array(), $error_codes );
 		$actual_stylesheets = array_values( $sanitizer->get_stylesheets() );
-		$this->assertEquals( '.sidebar1{display:none;}', $actual_stylesheets[0] );
-		$this->assertEquals( '.sidebar1.expanded{display:block;}', $actual_stylesheets[1] );
-		$this->assertEquals( '.sidebar2{visibility:hidden;}', $actual_stylesheets[2] );
-		$this->assertEquals( '.sidebar2.visible{display:block;}', $actual_stylesheets[3] );
+		$this->assertEquals( '.sidebar1{display:none}', $actual_stylesheets[0] );
+		$this->assertEquals( '.sidebar1.expanded{display:block}', $actual_stylesheets[1] );
+		$this->assertEquals( '.sidebar2{visibility:hidden}', $actual_stylesheets[2] );
+		$this->assertEquals( '.sidebar2.visible{display:block}', $actual_stylesheets[3] );
 		$this->assertEmpty( $actual_stylesheets[4] );
 	}
 
@@ -472,8 +472,10 @@ public function test_large_custom_css_and_rule_removal() {
 
 		$html  = '<html amp><head><meta charset="utf-8">';
 		$html .= '<style>.' . str_repeat( 'a', $custom_max_size - 50 ) . '{ color:red } .b{ color:blue; }</style>';
-		$html .= '<style>.b ' . str_repeat( 'c', $custom_max_size ) . '{ color:green }</style>';
-		$html .= '</head><body><span class="b">...</span></body></html>';
+		$html .= '<style>.b[data-value="' . str_repeat( 'c', $custom_max_size ) . '"] { color:green }</style>';
+		$html .= '<style>#nonexists { color:black; } #exists { color:white; }</style>';
+		$html .= '<style>div { color:black; } span { color:white; } </style>';
+		$html .= '</head><body><span class="b">...</span><span id="exists"></span></body></html>';
 		$dom   = AMP_DOM_Utils::get_dom( $html );
 
 		$error_codes = array();
@@ -486,7 +488,11 @@ public function test_large_custom_css_and_rule_removal() {
 		$sanitizer->sanitize();
 
 		$this->assertEquals(
-			array( '.b{color:blue;}' ),
+			array(
+				'.b{color:blue}',
+				'#exists{color:white}',
+				'span{color:white}',
+			),
 			array_values( $sanitizer->get_stylesheets() )
 		);
 
@@ -515,7 +521,7 @@ public function test_relative_background_url_handling() {
 		$stylesheet = $actual_stylesheets[0];
 
 		$this->assertNotContains( '../images/spinner', $stylesheet );
-		$this->assertContains( sprintf( '.spinner{background-image:url("%s");', admin_url( 'images/spinner-2x.gif' ) ), $stylesheet );
+		$this->assertContains( sprintf( '.spinner{background-image:url("%s")', admin_url( 'images/spinner-2x.gif' ) ), $stylesheet );
 	}
 
 	/**
@@ -536,7 +542,7 @@ public function get_keyframe_data() {
 		return array(
 			'style_amp_keyframes'              => array(
 				'<style amp-keyframes>@keyframes anim1 { from { opacity:0.0 } to { opacity:0.5 } } @media (min-width: 600px) {@keyframes anim1 { from { opacity:0.5 } to { opacity:1.0 } } }</style>',
-				'<style amp-keyframes="">@keyframes anim1{from{opacity:0;}to{opacity:.5;}}@media (min-width: 600px){@keyframes anim1{from{opacity:.5;}to{opacity:1;}}}</style>',
+				'<style amp-keyframes="">@keyframes anim1{from{opacity:0}to{opacity:.5}}@media (min-width: 600px){@keyframes anim1{from{opacity:.5}to{opacity:1}}}</style>',
 				array(),
 			),
 
@@ -554,13 +560,13 @@ public function get_keyframe_data() {
 
 			'blacklisted_and_whitelisted_keyframe_properties' => array(
 				'<style amp-keyframes>@keyframes anim1 { 50% { width: 50%; animation-timing-function: ease; opacity: 0.5; height:10%; offset-distance: 50%; visibility: visible; transform: rotate(0.5turn); -webkit-transform: rotate(0.5turn); color:red; } }</style>',
-				'<style amp-keyframes="">@keyframes anim1{50%{animation-timing-function:ease;opacity:.5;offset-distance:50%;visibility:visible;transform:rotate(.5 turn);-webkit-transform:rotate(.5 turn);}}</style>',
+				'<style amp-keyframes="">@keyframes anim1{50%{animation-timing-function:ease;opacity:.5;offset-distance:50%;visibility:visible;transform:rotate(.5 turn);-webkit-transform:rotate(.5 turn)}}</style>',
 				array( 'illegal_css_property', 'illegal_css_property', 'illegal_css_property' ),
 			),
 
 			'style_amp_keyframes_with_disallowed_rules' => array(
 				'<style amp-keyframes>body { color:red; opacity:1; } @keyframes anim1 { 50% { opacity:0.5 !important; } } @font-face { font-family: "Open Sans"; src: url("/fonts/OpenSans-Regular-webfont.woff2") format("woff2"); }</style>',
-				'<style amp-keyframes="">@keyframes anim1{50%{opacity:.5;}}</style>',
+				'<style amp-keyframes="">@keyframes anim1{50%{opacity:.5}}</style>',
 				array( 'unrecognized_css', 'illegal_css_important', 'illegal_css_at_rule' ),
 			),
 		);
diff --git a/tests/test-class-amp-theme-support.php b/tests/test-class-amp-theme-support.php
index 7548a8a3ddd..1260242420d 100644
--- a/tests/test-class-amp-theme-support.php
+++ b/tests/test-class-amp-theme-support.php
@@ -1029,7 +1029,7 @@ public function test_prepare_response() {
 		$this->assertContains( '<meta charset="' . get_bloginfo( 'charset' ) . '">', $sanitized_html );
 		$this->assertContains( '<meta name="viewport" content="width=device-width,minimum-scale=1">', $sanitized_html );
 		$this->assertContains( '<style amp-boilerplate>', $sanitized_html );
-		$this->assertRegExp( '#<style amp-custom>.*?body{background:black;}.*?</style>#s', $sanitized_html );
+		$this->assertRegExp( '#<style amp-custom>.*?body{background:black}.*?</style>#s', $sanitized_html );
 		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0.js" async></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
 		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0/amp-list-latest.js" async custom-element="amp-list"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
 		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0/amp-mathml-latest.js" async custom-element="amp-mathml"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript