diff --git a/wp-admin/js/customize-controls.js b/wp-admin/js/customize-controls.js
index 38e8e1addd..4e3dd8b645 100644
--- a/wp-admin/js/customize-controls.js
+++ b/wp-admin/js/customize-controls.js
@@ -145,9 +145,17 @@
 				browser:   this.container.find('.upload'),
 				dropzone:  this.container.find('.upload-dropzone'),
 				success:   this.success,
+				plupload:  {},
 				params:    {}
 			}, this.uploader || {} );
 
+			if ( control.params.extensions ) {
+				control.uploader.plupload.filters = [{
+					title:      api.l10n.allowedFiles,
+					extensions: control.params.extensions
+				}];
+			}
+
 			if ( control.params.context )
 				control.uploader.params['post_data[context]'] = this.params.context;
 
diff --git a/wp-includes/class-wp-customize-control.php b/wp-includes/class-wp-customize-control.php
index df118a3419..677bba7011 100644
--- a/wp-includes/class-wp-customize-control.php
+++ b/wp-includes/class-wp-customize-control.php
@@ -402,6 +402,7 @@ class WP_Customize_Upload_Control extends WP_Customize_Control {
 	public $type    = 'upload';
 	public $removed = '';
 	public $context;
+	public $extensions;
 
 	/**
 	 * Enqueue control related scripts/styles.
@@ -425,6 +426,9 @@ class WP_Customize_Upload_Control extends WP_Customize_Control {
 
 		if ( $this->context )
 			$this->json['context'] = $this->context;
+
+		if ( $this->extensions )
+			$this->json['extensions'] = $this->extensions;
 	}
 
 	/**
@@ -456,6 +460,7 @@ class WP_Customize_Image_Control extends WP_Customize_Upload_Control {
 	public $type = 'image';
 	public $get_url;
 	public $statuses;
+	public $extensions = 'jpg,jpeg,gif,png';
 
 	protected $tabs = array();
 
diff --git a/wp-includes/script-loader.php b/wp-includes/script-loader.php
index a347b50dda..cfedccae96 100644
--- a/wp-includes/script-loader.php
+++ b/wp-includes/script-loader.php
@@ -313,6 +313,9 @@ function wp_default_scripts( &$scripts ) {
 		'cancel'    => __( 'Cancel' ),
 		'close'     => __( 'Close' ),
 		'cheatin'   => __( 'Cheatin’ uh?' ),
+
+		// Used for overriding the file types allowed in plupload.
+		'allowedFiles' => __( 'Allowed Files' ),
 	) );
 
 	$scripts->add( 'media-models', "/wp-includes/js/media-models$suffix.js", array( 'backbone', 'jquery' ), false, 1 );