diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index e763ad6..f1dd106 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -206,7 +206,7 @@ public function addTheme(Extension $theme) {
     if (isset($theme->info['engine'])) {
       $theme->engine = $theme->info['engine'];
     }
-    if (!empty($theme->info['base theme'])) {
+    if (isset($theme->info['base theme'])) {
       $theme->base_theme = $theme->info['base theme'];
     }
     $this->list[$theme->getName()] = $theme;
@@ -283,6 +283,10 @@ public function rebuildThemeData() {
       $theme->status = (int) isset($installed[$key]);
 
       $theme->info = $this->infoParser->parse($theme->getPathname()) + $defaults;
+      // Handle when 'base theme: false' is set in a theme .info.yml file.
+      if (empty($theme->info['base theme'])) {
+        unset($theme->info['base theme']);
+      }
 
       // Add the info file modification time, so it becomes available for
       // contributed modules to use for ordering theme lists.
diff --git a/core/modules/quickedit/quickedit.module b/core/modules/quickedit/quickedit.module
index 72bae26..9a34105 100644
--- a/core/modules/quickedit/quickedit.module
+++ b/core/modules/quickedit/quickedit.module
@@ -80,7 +80,7 @@ function quickedit_library_info_alter(&$libraries, $extension) {
       if (isset($theme) && $theme_path = drupal_get_path('theme', $theme)) {
         $info = system_get_info('theme', $theme);
         // Recurse to process base theme(s) first.
-        if (!empty($info['base theme'])) {
+        if (isset($info['base theme'])) {
           $alter_library($library, $info['base theme']);
         }
         if (isset($info['quickedit_stylesheets'])) {
diff --git a/core/modules/system/src/Controller/SystemController.php b/core/modules/system/src/Controller/SystemController.php
index 9fbc41e..8f6b58a 100644
--- a/core/modules/system/src/Controller/SystemController.php
+++ b/core/modules/system/src/Controller/SystemController.php
@@ -247,7 +247,7 @@ public function themesPage() {
         $theme->incompatible_region = !isset($theme->info['regions']['content']);
         $theme->incompatible_php = version_compare(phpversion(), $theme->info['php']) < 0;
         // Confirmed that the base theme is available.
-        $theme->incompatible_base = !empty($theme->info['base theme']) && !isset($themes[$theme->info['base theme']]);
+        $theme->incompatible_base = isset($theme->info['base theme']) && !isset($themes[$theme->info['base theme']]);
         // Confirm that the theme engine is available.
         $theme->incompatible_engine = isset($theme->info['engine']) && !isset($theme->owner);
       }