diff --git a/src/wp-admin/js/customize-controls.js b/src/wp-admin/js/customize-controls.js
index 91f5af1353..a23a130c0b 100644
--- a/src/wp-admin/js/customize-controls.js
+++ b/src/wp-admin/js/customize-controls.js
@@ -3333,7 +3333,7 @@
 		 * @param {object} attachment
 		 */
 		setImageFromAttachment: function( attachment ) {
-			var sizes = [ 'site_icon-32', 'thumbnail', 'full' ],
+			var sizes = [ 'site_icon-32', 'thumbnail', 'full' ], link,
 				icon;
 
 			_.each( sizes, function( size ) {
@@ -3347,8 +3347,13 @@
 			// Set the Customizer setting; the callback takes care of rendering.
 			this.setting( attachment.id );
 
+			if ( ! icon ) {
+				return;
+			}
+
 			// Update the icon in-browser.
-			$( 'link[sizes="32x32"]' ).attr( 'href', icon.url );
+			link = $( 'link[rel="icon"][sizes="32x32"]' );
+			link.attr( 'href', icon.url );
 		},
 
 		/**
@@ -3365,7 +3370,7 @@
 			this.params.attachment = {};
 			this.setting( '' );
 			this.renderContent(); // Not bound to setting change when emptying.
-			$( 'link[rel="icon"]' ).attr( 'href', '' );
+			$( 'link[rel="icon"][sizes="32x32"]' ).attr( 'href', '/favicon.ico' ); // Set to default.
 		}
 	});
 
diff --git a/src/wp-includes/general-template.php b/src/wp-includes/general-template.php
index 5174936de1..8e58b5cf49 100644
--- a/src/wp-includes/general-template.php
+++ b/src/wp-includes/general-template.php
@@ -2776,12 +2776,26 @@ function wp_site_icon() {
 		return;
 	}
 
-	$meta_tags = array(
-		sprintf( '<link rel="icon" href="%s" sizes="32x32" />', esc_url( get_site_icon_url( 32 ) ) ),
-		sprintf( '<link rel="icon" href="%s" sizes="192x192" />', esc_url( get_site_icon_url( 192 ) ) ),
-		sprintf( '<link rel="apple-touch-icon-precomposed" href="%s" />', esc_url( get_site_icon_url( 180 ) ) ),
-		sprintf( '<meta name="msapplication-TileImage" content="%s" />', esc_url( get_site_icon_url( 270 ) ) ),
-	);
+	$meta_tags = array();
+	$icon_32 = get_site_icon_url( 32 );
+	if ( empty( $icon_32 ) && is_customize_preview() ) {
+		$icon_32 = '/favicon.ico'; // Serve default favicon URL in customizer so element can be updated for preview.
+	}
+	if ( $icon_32 ) {
+		$meta_tags[] = sprintf( '<link rel="icon" href="%s" sizes="32x32" />', esc_url( $icon_32 ) );
+	}
+	$icon_192 = get_site_icon_url( 192 );
+	if ( $icon_192 ) {
+		$meta_tags[] = sprintf( '<link rel="icon" href="%s" sizes="192x192" />', esc_url( $icon_192 ) );
+	}
+	$icon_180 = get_site_icon_url( 180 );
+	if ( $icon_180 ) {
+		$meta_tags[] = sprintf( '<link rel="apple-touch-icon-precomposed" href="%s" />', esc_url( $icon_180 ) );
+	}
+	$icon_270 = get_site_icon_url( 270 );
+	if ( $icon_270 ) {
+		$meta_tags[] = sprintf( '<meta name="msapplication-TileImage" content="%s" />', esc_url( $icon_270 ) );
+	}
 
 	/**
 	 * Filters the site icon meta tags, so Plugins can add their own.
diff --git a/tests/phpunit/tests/general/template.php b/tests/phpunit/tests/general/template.php
index d650d1ddf2..16007cf9a9 100644
--- a/tests/phpunit/tests/general/template.php
+++ b/tests/phpunit/tests/general/template.php
@@ -23,7 +23,10 @@ class Tests_General_Template extends WP_UnitTestCase {
 	}
 
 	function tearDown() {
+		global $wp_customize;
 		$this->_remove_custom_logo();
+		$this->_remove_site_icon();
+		$wp_customize = null;
 
 		parent::tearDown();
 	}
@@ -51,7 +54,6 @@ class Tests_General_Template extends WP_UnitTestCase {
 		$this->_set_site_icon();
 		$this->expectOutputString( $this->site_icon_url );
 		site_icon_url();
-		$this->_remove_site_icon();
 	}
 
 	/**
@@ -117,8 +119,6 @@ class Tests_General_Template extends WP_UnitTestCase {
 
 		$this->expectOutputString( $output );
 		wp_site_icon();
-
-		$this->_remove_site_icon();
 	}
 
 	/**
@@ -143,8 +143,51 @@ class Tests_General_Template extends WP_UnitTestCase {
 		add_filter( 'site_icon_meta_tags', array( $this, '_custom_site_icon_meta_tag' ) );
 		wp_site_icon();
 		remove_filter( 'site_icon_meta_tags', array( $this, '_custom_site_icon_meta_tag' ) );
+	}
 
-		$this->_remove_site_icon();
+	/**
+	 * @group site_icon
+	 * @ticket 38377
+	 */
+	function test_customize_preview_wp_site_icon_empty() {
+		global $wp_customize;
+		wp_set_current_user( $this->factory()->user->create( array( 'role' => 'administrator' ) ) );
+
+		require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+		$wp_customize = new WP_Customize_Manager();
+		$wp_customize->register_controls();
+		$wp_customize->start_previewing_theme();
+
+		$this->expectOutputString( '<link rel="icon" href="/favicon.ico" sizes="32x32" />' . "\n" );
+		wp_site_icon();
+	}
+
+	/**
+	 * @group site_icon
+	 * @ticket 38377
+	 */
+	function test_customize_preview_wp_site_icon_dirty() {
+		global $wp_customize;
+		wp_set_current_user( $this->factory()->user->create( array( 'role' => 'administrator' ) ) );
+
+		require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+		$wp_customize = new WP_Customize_Manager();
+		$wp_customize->register_controls();
+		$wp_customize->start_previewing_theme();
+
+		$attachment_id = $this->_insert_attachment();
+		$wp_customize->set_post_value( 'site_icon', $attachment_id );
+		$wp_customize->get_setting( 'site_icon' )->preview();
+		$output = array(
+			sprintf( '<link rel="icon" href="%s" sizes="32x32" />', esc_url( wp_get_attachment_image_url( $attachment_id, 32 ) ) ),
+			sprintf( '<link rel="icon" href="%s" sizes="192x192" />', esc_url( wp_get_attachment_image_url( $attachment_id, 192 ) ) ),
+			sprintf( '<link rel="apple-touch-icon-precomposed" href="%s" />', esc_url( wp_get_attachment_image_url( $attachment_id, 180 ) ) ),
+			sprintf( '<meta name="msapplication-TileImage" content="%s" />', esc_url( wp_get_attachment_image_url( $attachment_id, 270 ) ) ),
+			'',
+		);
+		$output = implode( "\n", $output );
+		$this->expectOutputString( $output );
+		wp_site_icon();
 	}
 
 	/**