diff --git src/wp-admin/js/customize-controls.js src/wp-admin/js/customize-controls.js
index e354d0d..2cd47f1 100644
--- src/wp-admin/js/customize-controls.js
+++ src/wp-admin/js/customize-controls.js
@@ -3336,7 +3336,7 @@
 		 * @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 ) {
@@ -3350,8 +3350,13 @@
 			// 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 );
 		},
 
 		/**
@@ -3368,7 +3373,7 @@
 			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 src/wp-includes/general-template.php src/wp-includes/general-template.php
index 5b36272..e91db54 100644
--- src/wp-includes/general-template.php
+++ src/wp-includes/general-template.php
@@ -2780,12 +2780,26 @@ 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.