diff --git a/core/modules/system/src/Form/ModulesListForm.php b/core/modules/system/src/Form/ModulesListForm.php
index e4ccdfb9b5..fd60136c53 100644
--- a/core/modules/system/src/Form/ModulesListForm.php
+++ b/core/modules/system/src/Form/ModulesListForm.php
@@ -21,7 +21,6 @@
 use Drupal\Core\Url;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
-
 /**
  * Provides module installation interface.
  *
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 4cf4dba37b..678ea6bb17 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -294,13 +294,7 @@ function template_preprocess_system_themes_page(&$variables) {
       // Make sure to provide feedback on compatibility.
       $current_theme['incompatible'] = '';
       if (!empty($theme->incompatible_core)) {
-        if (isset($theme->info['core'])) {
-          $current_theme['incompatible'] = t("This theme is not compatible with Drupal @core_version. It is only compatible with Drupal versions that satisfy this constraint: @core_constraint", ['@core_version' => \Drupal::VERSION, '@core_constraint' => $theme->info['core']]);
-        }
-        else {
-          $current_theme['incompatible'] = t("This theme must declare a 'core' value in its .info.yml file.");
-        }
-
+        $current_theme['incompatible'] = t("This theme is not compatible with Drupal @core_version. Check that the .info.yml file contains a compatible 'core' value.", ['@core_version' => \Drupal::VERSION, '@core_constraint' => $theme->info['core']]);
       }
       elseif (!empty($theme->incompatible_region)) {
         $current_theme['incompatible'] = t("This theme is missing a 'content' region.");
diff --git a/core/modules/system/tests/src/Functional/System/ThemeTest.php b/core/modules/system/tests/src/Functional/System/ThemeTest.php
index a107459ff6..02952f6656 100644
--- a/core/modules/system/tests/src/Functional/System/ThemeTest.php
+++ b/core/modules/system/tests/src/Functional/System/ThemeTest.php
@@ -368,7 +368,7 @@ public function testInvalidTheme() {
     $this->assertText(t('This theme requires the base theme @base_theme to operate correctly.', ['@base_theme' => 'test_invalid_basetheme']));
     $this->assertText(t('This theme requires the theme engine @theme_engine to operate correctly.', ['@theme_engine' => 'not_real_engine']));
     // Check for the error text of a theme with the wrong core version.
-    $this->assertText("This theme is not compatible with Drupal 8.x. Check that the .info.yml file contains the correct 'core' value.");
+    $this->assertText("This theme is not compatible with Drupal " . \Drupal::VERSION . ". Check that the .info.yml file contains a compatible 'core' value.");
     // Check for the error text of a theme without a content region.
     $this->assertText("This theme is missing a 'content' region.");
   }