diff --git a/lib/class-wp-theme-json.php b/lib/class-wp-theme-json.php
index 716113f371def7..32f3513fff8b9b 100644
--- a/lib/class-wp-theme-json.php
+++ b/lib/class-wp-theme-json.php
@@ -791,7 +791,7 @@ private static function compute_preset_classes( $settings, $selector ) {
 						array(
 							array(
 								'name'  => $class['property_name'],
-								'value' => $value[ $preset['value_key'] ],
+								'value' => $value[ $preset['value_key'] ] . ' !important',
 							),
 						)
 					);
diff --git a/phpunit/class-wp-theme-json-test.php b/phpunit/class-wp-theme-json-test.php
index a74c88a51dcede..81e77bcb234692 100644
--- a/phpunit/class-wp-theme-json-test.php
+++ b/phpunit/class-wp-theme-json-test.php
@@ -280,11 +280,11 @@ function test_get_stylesheet() {
 		);
 
 		$this->assertEquals(
-			':root{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}:root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey;}.has-grey-background-color{background-color: grey;}',
+			':root{--wp--preset--color--grey: grey;--wp--preset--font-family--small: 14px;--wp--preset--font-family--big: 41px;}.wp-block-group{--wp--custom--base-font: 16;--wp--custom--line-height--small: 1.2;--wp--custom--line-height--medium: 1.4;--wp--custom--line-height--large: 1.8;}:root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}',
 			$theme_json->get_stylesheet()
 		);
 		$this->assertEquals(
-			':root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey;}.has-grey-background-color{background-color: grey;}',
+			':root{--wp--style--color--link: #111;color: var(--wp--preset--color--grey);}.wp-block-group{padding-top: 12px;padding-bottom: 24px;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}',
 			$theme_json->get_stylesheet( 'block_styles' )
 		);
 		$this->assertEquals(
@@ -319,15 +319,51 @@ function test_get_stylesheet_preset_rules_come_after_block_rules() {
 		);
 
 		$this->assertEquals(
-			'.wp-block-group{--wp--preset--color--grey: grey;}.wp-block-group{color: red;}.wp-block-group.has-grey-color{color: grey;}.wp-block-group.has-grey-background-color{background-color: grey;}',
+			'.wp-block-group{--wp--preset--color--grey: grey;}.wp-block-group{color: red;}.wp-block-group.has-grey-color{color: grey !important;}.wp-block-group.has-grey-background-color{background-color: grey !important;}',
 			$theme_json->get_stylesheet()
 		);
 		$this->assertEquals(
-			'.wp-block-group{color: red;}.wp-block-group.has-grey-color{color: grey;}.wp-block-group.has-grey-background-color{background-color: grey;}',
+			'.wp-block-group{color: red;}.wp-block-group.has-grey-color{color: grey !important;}.wp-block-group.has-grey-background-color{background-color: grey !important;}',
 			$theme_json->get_stylesheet( 'block_styles' )
 		);
 	}
 
+	public function test_get_stylesheet_preset_values_are_marked_as_important() {
+		$theme_json = new WP_Theme_JSON(
+			array(
+				'settings' => array(
+					'defaults' => array(
+						'color' => array(
+							'palette' => array(
+								array(
+									'slug'  => 'grey',
+									'color' => 'grey',
+								),
+							),
+						),
+					),
+				),
+				'styles'   => array(
+					'core/post-title/h2' => array(
+						'color'      => array(
+							'text'       => 'red',
+							'background' => 'blue',
+						),
+						'typography' => array(
+							'fontSize'   => '12px',
+							'lineHeight' => '1.3',
+						),
+					),
+				),
+			)
+		);
+
+		$this->assertEquals(
+			':root{--wp--preset--color--grey: grey;}h2.wp-block-post-title{background-color: blue;color: red;font-size: 12px;line-height: 1.3;}.has-grey-color{color: grey !important;}.has-grey-background-color{background-color: grey !important;}',
+			$theme_json->get_stylesheet()
+		);
+	}
+
 	public function test_merge_incoming_data() {
 		$root_name = WP_Theme_JSON::ROOT_BLOCK_NAME;
 		$initial   = array(