diff --git a/css/src/modal.css b/css/src/modal.css
index 98ba438b8e1..e3484058d3e 100644
--- a/css/src/modal.css
+++ b/css/src/modal.css
@@ -82,7 +82,7 @@
 }
 
 .yoast-gutenberg-modal .components-modal__content .components-modal__header {
-	border-bottom-color: #e2e8f0 !important;
+	border-bottom: 1px solid #e2e8f0 !important;
 }
 
 .yoast-gutenberg-modal .components-modal__icon-container {
diff --git a/package.json b/package.json
index 97b608e0254..4ec7ed46108 100644
--- a/package.json
+++ b/package.json
@@ -83,7 +83,7 @@
     "typescript": "^4.2.4"
   },
   "yoast": {
-    "pluginVersion": "21.5-RC3"
+    "pluginVersion": "21.5-RC4"
   },
   "version": "0.0.0"
 }
diff --git a/wp-seo-main.php b/wp-seo-main.php
index ccfe2889477..34bf056e95a 100644
--- a/wp-seo-main.php
+++ b/wp-seo-main.php
@@ -15,7 +15,7 @@
  * {@internal Nobody should be able to overrule the real version number as this can cause
  *            serious issues with the options, so no if ( ! defined() ).}}
  */
-define( 'WPSEO_VERSION', '21.5-RC3' );
+define( 'WPSEO_VERSION', '21.5-RC4' );
 
 
 if ( ! defined( 'WPSEO_PATH' ) ) {
diff --git a/wp-seo.php b/wp-seo.php
index 146d3cd7c56..e1cfb103a6d 100644
--- a/wp-seo.php
+++ b/wp-seo.php
@@ -8,7 +8,7 @@
  *
  * @wordpress-plugin
  * Plugin Name: Yoast SEO
- * Version:     21.5-RC3
+ * Version:     21.5-RC4
  * Plugin URI:  https://yoa.st/1uj
  * Description: The first true all-in-one SEO solution for WordPress, including on-page content analysis, XML sitemaps and much more.
  * Author:      Team Yoast