diff --git a/wp-includes/post.php b/wp-includes/post.php
index 3d1227ff9a..1e5d3a27f0 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -1342,9 +1342,9 @@ function register_post_type( $post_type, $args = array() ) {
 	$post_type = sanitize_key( $post_type );
 	$args->name = $post_type;
 
-	if ( strlen( $post_type ) > 20 ) {
-		_doing_it_wrong( __FUNCTION__, __( 'Post types cannot exceed 20 characters in length' ), '4.0' );
-		return new WP_Error( 'post_type_too_long', __( 'Post types cannot exceed 20 characters in length' ) );
+	if ( empty( $post_type ) || strlen( $post_type ) > 20 ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Post type names must be between 1 and 20 characters in length.' ), '4.2' );
+		return new WP_Error( 'post_type_length_invalid', __( 'Post type names must be between 1 and 20 characters in length.' ) );
 	}
 
 	// If not set, default to the setting for public.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 6802788ef2..d48b34f2c0 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31449';
+$wp_version = '4.2-alpha-31450';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.