diff --git a/src/wp-includes/user.php b/src/wp-includes/user.php
index ba63576fd6..ee7c87f8a6 100644
--- a/src/wp-includes/user.php
+++ b/src/wp-includes/user.php
@@ -2123,16 +2123,10 @@ function wp_insert_user( $userdata ) {
 		return new WP_Error( 'user_login_too_long', __( 'Username may not be longer than 60 characters.' ) );
 	}
 
-	// Username must be unique.
 	if ( ! $update && username_exists( $user_login ) ) {
 		return new WP_Error( 'existing_user_login', __( 'Sorry, that username already exists!' ) );
 	}
 
-	// Username must not match an existing user email.
-	if ( email_exists( $user_login ) ) {
-		return new WP_Error( 'existing_user_email_as_login', __( 'Sorry, that username is not available.' ) );
-	}
-
 	/**
 	 * Filters the list of disallowed usernames.
 	 *
@@ -3346,8 +3340,6 @@ function register_new_user( $user_login, $user_email ) {
 		$sanitized_user_login = '';
 	} elseif ( username_exists( $sanitized_user_login ) ) {
 		$errors->add( 'username_exists', __( '<strong>Error:</strong> This username is already registered. Please choose another one.' ) );
-	} elseif ( email_exists( $sanitized_user_login ) ) {
-		$errors->add( 'username_exists_as_email', __( '<strong>Error:</strong> This username is not available. Please choose another one.' ) );
 	} else {
 		/** This filter is documented in wp-includes/user.php */
 		$illegal_user_logins = (array) apply_filters( 'illegal_user_logins', array() );
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index 24496c7895..7157a00cfa 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -897,24 +897,6 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertSame( 'user_login_too_long', $u->get_error_code() );
 	}
 
-	/**
-	 * @ticket 57394
-	 */
-	public function test_wp_insert_user_should_reject_user_login_that_matches_existing_user_email() {
-		$existing_email = get_option( 'admin_email' );
-		$user_id        = wp_insert_user(
-			array(
-				'user_login'    => $existing_email,
-				'user_email'    => 'whatever@example.com',
-				'user_pass'     => 'whatever',
-				'user_nicename' => 'whatever',
-			)
-		);
-
-		$this->assertWPError( $user_id );
-		$this->assertSame( 'existing_user_email_as_login', $user_id->get_error_code() );
-	}
-
 	/**
 	 * @ticket 33793
 	 */