diff --git a/mailpoet/lib/EmailEditor/Engine/SettingsController.php b/mailpoet/lib/EmailEditor/Engine/SettingsController.php
index 4fa127efcb..f2ca6170b8 100644
--- a/mailpoet/lib/EmailEditor/Engine/SettingsController.php
+++ b/mailpoet/lib/EmailEditor/Engine/SettingsController.php
@@ -191,12 +191,17 @@ class SettingsController {
   }
 
   public function getStylesheetForRendering(): string {
-    $settings = $this->getTheme()->get_settings();
+    $coreThemeSettings = \WP_Theme_JSON_Resolver::get_core_data()->get_settings();
+    $emailThemeSettings = $this->getTheme()->get_settings();
     $css = '';
     // Font family classes
-    foreach ($settings['typography']['fontFamilies']['theme'] as $fontFamily) {
+    foreach ($emailThemeSettings['typography']['fontFamilies']['theme'] as $fontFamily) {
       $css .= ".has-{$fontFamily['slug']}-font-family { font-family: {$fontFamily['fontFamily']}; } \n";
     }
+    // Font size classes
+    foreach ($coreThemeSettings['typography']['fontSizes']['default'] as $fontSize) {
+      $css .= ".has-{$fontSize['slug']}-font-size { font-size: {$fontSize['size']}; } \n";
+    }
     return $css;
   }
 
diff --git a/mailpoet/tests/integration/EmailEditor/Engine/SettingsControllerTest.php b/mailpoet/tests/integration/EmailEditor/Engine/SettingsControllerTest.php
index 7dd1edafdb..d1a447608a 100644
--- a/mailpoet/tests/integration/EmailEditor/Engine/SettingsControllerTest.php
+++ b/mailpoet/tests/integration/EmailEditor/Engine/SettingsControllerTest.php
@@ -11,7 +11,7 @@ class SettingsControllerTest extends \MailPoetTest {
     $this->settingsController = $this->diContainer->get(SettingsController::class);
   }
 
-  public function testItGeneratesCssStylesForThemeWithFontFamilies() {
+  public function testItGeneratesCssStylesForRenderer() {
     $css = $this->settingsController->getStylesheetForRendering();
     verify($css)->stringContainsString('.has-arial-font-family');
     verify($css)->stringContainsString('.has-comic-sans-ms-font-family');
@@ -35,6 +35,11 @@ class SettingsControllerTest extends \MailPoetTest {
     verify($css)->stringContainsString('.has-raleway-font-family');
     verify($css)->stringContainsString('.has-permanent-marker-font-family');
     verify($css)->stringContainsString('.has-pacifico-font-family');
+
+    verify($css)->stringContainsString('.has-small-font-size');
+    verify($css)->stringContainsString('.has-medium-font-size');
+    verify($css)->stringContainsString('.has-large-font-size');
+    verify($css)->stringContainsString('.has-x-large-font-size');
   }
 
   public function testItCanTranslateFontSizeSlug() {