diff --git a/src/wp-includes/js/wp-embed.js b/src/wp-includes/js/wp-embed.js
index 985f0b801d..660558e03b 100644
--- a/src/wp-includes/js/wp-embed.js
+++ b/src/wp-includes/js/wp-embed.js
@@ -1,3 +1,12 @@
+/**
+ * WordPress inline HTML embed
+ *
+ * @since 4.4.0
+ *
+ * This file cannot have ampersands in it. This is to ensure
+ * it can be embedded in older versions of WordPress.
+ * See https://core.trac.wordpress.org/changeset/35708.
+ */
 (function ( window, document ) {
 	'use strict';
 
diff --git a/tests/phpunit/tests/oembed/template.php b/tests/phpunit/tests/oembed/template.php
index ca07035b23..9121670185 100644
--- a/tests/phpunit/tests/oembed/template.php
+++ b/tests/phpunit/tests/oembed/template.php
@@ -253,4 +253,52 @@ class Tests_Embed_Template extends WP_UnitTestCase {
 
 		$this->assertTrue( wp_script_is( 'wp-embed' ) );
 	}
+
+	/**
+	 * @ticket 34698
+	 */
+	function test_js_no_ampersands() {
+		$this->assertNotContains( '&', file_get_contents( ABSPATH . WPINC . '/js/wp-embed.js' ) );
+	}
+
+	/**
+	 * @ticket 34698
+	 *
+	 * @depends test_js_no_ampersands
+	 *
+	 * The previous test confirms that no ampersands exist in src/wp-includes/js/wp-embed.js.
+	 * However, we must also confirm that UglifyJS does not add ampersands during its
+	 * optimizations (which we tweak to avoid, but indirectly -- understandably, there's
+	 * no "don't add ampersands to my JavaScript file" option).
+	 *
+	 * So this test checks for ampersands in build/wp-includes/js/wp-embed.min.js.
+	 * In many cases, this file will not exist; in those cases, we simply skip the test.
+	 *
+	 * So when would it be run? We have Travis CI run `grunt test` which then runs, in order,
+	 * `qunit:compiled` (which runs the build) and then `phpunit`. Thus, this test will at least be
+	 * run during continuous integration.
+	 *
+	 * However, we need to verify that `qunit:compiled` runs before `phpunit`. So this test also
+	 * does a cheap check for a registered Grunt task called `test` that contains both
+	 * `qunit:compiled` and `phpunit`, in that order.
+	 *
+	 * One final failsafe: The Gruntfile.js assertion takes place before checking for the existence
+	 * of wp-embed.min.js. If the Grunt tasks are significantly refactored later, it could indicate
+	 * that wp-embed.min.js doesn't exist anymore. We wouldn't want the test to silently become one
+	 * that is always skipped, and thus useless.
+	 */
+	function test_js_no_ampersands_in_compiled() {
+		$gruntfile = file_get_contents( dirname( ABSPATH ) . '/Gruntfile.js' );
+
+		// Confirm this file *should* exist, otherwise this test will always be skipped.
+		$test = '/grunt.registerTask\(\s*\'test\',.*\'qunit:compiled\'.*\'phpunit\'/';
+		$this->assertTrue( (bool) preg_match( $test, $gruntfile ) );
+
+		$file = dirname( ABSPATH ) . '/build/' . WPINC . '/js/wp-embed.min.js';
+		if ( ! file_exists( $file ) ) {
+			$this->markTestSkipped( "This test is for the compiled wp-embed.min.js file." );
+		}
+		$this->assertNotContains( '&', file_get_contents( $file ) );
+	}
+
 }