diff --git a/lib/block-supports/background.php b/lib/block-supports/background.php
index a32ee72fd90c6d..bf5945312348b9 100644
--- a/lib/block-supports/background.php
+++ b/lib/block-supports/background.php
@@ -78,8 +78,11 @@ function gutenberg_render_background_support( $block_content, $block ) {
 			$existing_style = $tags->get_attribute( 'style' );
 			$updated_style  = '';
 
-			if ( ! empty( $existing_style ) && ! str_ends_with( $existing_style, ';' ) ) {
-				$updated_style = $existing_style . '; ';
+			if ( ! empty( $existing_style ) ) {
+				$updated_style = $existing_style;
+				if ( ! str_ends_with( $existing_style, ';' ) ) {
+					$updated_style .= ';';
+				}
 			}
 
 			$updated_style .= $styles['css'];
diff --git a/phpunit/block-supports/background-test.php b/phpunit/block-supports/background-test.php
new file mode 100644
index 00000000000000..bdcfc02f551a7f
--- /dev/null
+++ b/phpunit/block-supports/background-test.php
@@ -0,0 +1,187 @@
+<?php
+
+/**
+ * Test the background block support.
+ *
+ * @package Gutenberg
+ */
+class WP_Block_Supports_Background_Test extends WP_UnitTestCase {
+	/**
+	 * @var string|null
+	 */
+	private $test_block_name;
+
+	/**
+	 * Theme root directory.
+	 *
+	 * @var string
+	 */
+	private $theme_root;
+
+	/**
+	 * Original theme directory.
+	 *
+	 * @var string
+	 */
+	private $orig_theme_dir;
+
+	public function set_up() {
+		parent::set_up();
+		$this->test_block_name = null;
+		$this->theme_root      = realpath( __DIR__ . '/../data/themedir1' );
+		$this->orig_theme_dir  = $GLOBALS['wp_theme_directories'];
+
+		// /themes is necessary as theme.php functions assume /themes is the root if there is only one root.
+		$GLOBALS['wp_theme_directories'] = array( WP_CONTENT_DIR . '/themes', $this->theme_root );
+
+		add_filter( 'theme_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'stylesheet_root', array( $this, 'filter_set_theme_root' ) );
+		add_filter( 'template_root', array( $this, 'filter_set_theme_root' ) );
+
+		// Clear caches.
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+		WP_Style_Engine_CSS_Rules_Store::remove_all_stores();
+	}
+
+	public function tear_down() {
+		$GLOBALS['wp_theme_directories'] = $this->orig_theme_dir;
+
+		// Clear up the filters to modify the theme root.
+		remove_filter( 'theme_root', array( $this, 'filter_set_theme_root' ) );
+		remove_filter( 'stylesheet_root', array( $this, 'filter_set_theme_root' ) );
+		remove_filter( 'template_root', array( $this, 'filter_set_theme_root' ) );
+
+		wp_clean_themes_cache();
+		unset( $GLOBALS['wp_themes'] );
+		WP_Style_Engine_CSS_Rules_Store::remove_all_stores();
+		unregister_block_type( $this->test_block_name );
+		$this->test_block_name = null;
+		parent::tear_down();
+	}
+
+	public function filter_set_theme_root() {
+		return $this->theme_root;
+	}
+
+	/**
+	 * Tests that background image block support works as expected.
+	 *
+	 * @covers ::gutenberg_render_background_support
+	 *
+	 * @dataProvider data_background_block_support
+	 *
+	 * @param string $theme_name          The theme to switch to.
+	 * @param string $block_name          The test block name to register.
+	 * @param mixed  $background_settings The background block support settings.
+	 * @param mixed  $background_style    The background styles within the block attributes.
+	 * @param string $expected_wrapper    Expected markup for the block wrapper.
+	 * @param string $wrapper             Existing markup for the block wrapper.
+	 */
+	public function test_background_block_support( $theme_name, $block_name, $background_settings, $background_style, $expected_wrapper, $wrapper ) {
+		switch_theme( $theme_name );
+		$this->test_block_name = $block_name;
+
+		register_block_type(
+			$this->test_block_name,
+			array(
+				'api_version' => 2,
+				'attributes'  => array(
+					'style' => array(
+						'type' => 'object',
+					),
+				),
+				'supports'    => array(
+					'background' => $background_settings,
+				),
+			)
+		);
+
+		$block = array(
+			'blockName' => $block_name,
+			'attrs'     => array(
+				'style' => array(
+					'background' => $background_style,
+				),
+			),
+		);
+
+		$actual = gutenberg_render_background_support( $wrapper, $block );
+
+		$this->assertEquals(
+			$expected_wrapper,
+			$actual,
+			'Background block wrapper markup should be correct'
+		);
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array
+	 */
+	public function data_background_block_support() {
+		return array(
+			'background image style is applied' => array(
+				'theme_name'          => 'block-theme-child-with-fluid-typography',
+				'block_name'          => 'test/background-rules-are-output',
+				'background_settings' => array(
+					'backgroundImage' => true,
+				),
+				'background_style'    => array(
+					'backgroundImage' => array(
+						'url'    => 'https://example.com/image.jpg',
+						'source' => 'file',
+					),
+				),
+				'expected_wrapper'    => '<div style="background-image:url(&#039;https://example.com/image.jpg&#039;);background-size:cover;">Content</div>',
+				'wrapper'             => '<div>Content</div>',
+			),
+			'background image style is appended if a style attribute already exists' => array(
+				'theme_name'          => 'block-theme-child-with-fluid-typography',
+				'block_name'          => 'test/background-rules-are-output',
+				'background_settings' => array(
+					'backgroundImage' => true,
+				),
+				'background_style'    => array(
+					'backgroundImage' => array(
+						'url'    => 'https://example.com/image.jpg',
+						'source' => 'file',
+					),
+				),
+				'expected_wrapper'    => '<div classname="wp-block-test" style="color: red;background-image:url(&#039;https://example.com/image.jpg&#039;);background-size:cover;">Content</div>',
+				'wrapper'             => '<div classname="wp-block-test" style="color: red">Content</div>',
+			),
+			'background image style is appended if a style attribute containing multiple styles already exists' => array(
+				'theme_name'          => 'block-theme-child-with-fluid-typography',
+				'block_name'          => 'test/background-rules-are-output',
+				'background_settings' => array(
+					'backgroundImage' => true,
+				),
+				'background_style'    => array(
+					'backgroundImage' => array(
+						'url'    => 'https://example.com/image.jpg',
+						'source' => 'file',
+					),
+				),
+				'expected_wrapper'    => '<div classname="wp-block-test" style="color: red;font-size: 15px;background-image:url(&#039;https://example.com/image.jpg&#039;);background-size:cover;">Content</div>',
+				'wrapper'             => '<div classname="wp-block-test" style="color: red;font-size: 15px;">Content</div>',
+			),
+			'background image style is not applied if the block does not support background image' => array(
+				'theme_name'          => 'block-theme-child-with-fluid-typography',
+				'block_name'          => 'test/background-rules-are-not-output',
+				'background_settings' => array(
+					'backgroundImage' => false,
+				),
+				'background_style'    => array(
+					'backgroundImage' => array(
+						'url'    => 'https://example.com/image.jpg',
+						'source' => 'file',
+					),
+				),
+				'expected_wrapper'    => '<div>Content</div>',
+				'wrapper'             => '<div>Content</div>',
+			),
+		);
+	}
+}