diff --git a/wp-content/themes/twentyseventeen/assets/css/ie9.css b/wp-content/themes/twentyseventeen/assets/css/ie9.css
new file mode 100644
index 0000000000..24c8905162
--- /dev/null
+++ b/wp-content/themes/twentyseventeen/assets/css/ie9.css
@@ -0,0 +1,37 @@
+/*
+Theme Name: Twenty Seventeen
+Description: IE9 specific styles.
+*/
+
+.has-header-image.twentyseventeen-front-page .custom-header,
+.has-header-image.home.blog .custom-header {
+	height: 300px;
+}
+
+.has-header-image .custom-header-image img,
+.has-header-image .custom-header-image video,
+.has-header-image .custom-header-image iframe {
+	min-width: 100%;
+}
+
+@media screen and (min-width: 30em) {
+
+	.has-header-image.twentyseventeen-front-page .custom-header,
+	.has-header-image.home.blog .custom-header,
+	.twentyseventeen-front-page.has-header-image .custom-header-image,
+	.home.blog.has-header-image .custom-header-image,
+	.panel-image {
+		height: 700px;
+	}
+}
+
+@media screen and (min-width: 48em) {
+
+	.has-header-image.twentyseventeen-front-page .custom-header,
+	.has-header-image.home.blog .custom-header,
+	.twentyseventeen-front-page.has-header-image .custom-header-image,
+	.home.blog.has-header-image .custom-header-image,
+	.panel-image {
+		height: 1000px;
+	}
+}
diff --git a/wp-content/themes/twentyseventeen/functions.php b/wp-content/themes/twentyseventeen/functions.php
index 7b4b34e989..5c176f2a88 100644
--- a/wp-content/themes/twentyseventeen/functions.php
+++ b/wp-content/themes/twentyseventeen/functions.php
@@ -356,6 +356,12 @@ function twentyseventeen_scripts() {
 		wp_enqueue_style( 'twentyseventeen-colors-dark', get_theme_file_uri( '/assets/css/colors-dark.css' ), array( 'twentyseventeen-style' ), '1.0' );
 	}
 
+	// Load the Internet Explorer 9 specific stylesheet, to fix display issues in the Customizer.
+	if ( is_customize_preview() ) {
+		wp_enqueue_style( 'twentyseventeen-ie9', get_theme_file_uri( '/assets/css/ie9.css' ), array( 'twentyseventeen-style' ), '1.0' );
+		wp_style_add_data( 'twentyseventeen-ie9', 'conditional', 'IE 9' );
+	}
+
 	// Load the Internet Explorer 8 specific stylesheet.
 	wp_enqueue_style( 'twentyseventeen-ie8', get_theme_file_uri( '/assets/css/ie8.css' ), array( 'twentyseventeen-style' ), '1.0' );
 	wp_style_add_data( 'twentyseventeen-ie8', 'conditional', 'lt IE 9' );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 89a95fedab..eef1cab1d6 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta3-39214';
+$wp_version = '4.7-beta3-39215';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.