diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 6c9bb8f..c8dcc97 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -147,6 +147,7 @@ function drupal_find_theme_functions($cache, $prefixes) {
               'function' => $match,
               $arg_name => $info[$arg_name],
               'base hook' => $hook,
+              'incomplete preprocess functions' => TRUE,
             );
           }
         }
@@ -262,6 +263,7 @@ function drupal_find_theme_templates($cache, $extension, $path) {
             'path' => dirname($files[$match]->uri),
             $arg_name => $info[$arg_name],
             'base hook' => $hook,
+            'incomplete preprocess functions' => TRUE,
           );
         }
       }
diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index 33d880b..8fdc4fd 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -579,6 +579,43 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
   }
 
   /**
+   * Completes the definition of the requested suggestion hook.
+   *
+   * @param string $hook
+   *   The name of the suggestion hook to complete.
+   * @param array $cache
+   *   The theme registry.
+   */
+  protected function completeSuggestion($hook, array &$cache) {
+    $previous_hook = $hook;
+    $incomplete_previous_hook = array();
+    while ((!isset($cache[$previous_hook]) || isset($cache[$previous_hook]['incomplete preprocess functions']))
+      && $pos = strrpos($previous_hook, '__')) {
+      if (isset($cache[$previous_hook]) && !$incomplete_previous_hook && isset($cache[$previous_hook]['incomplete preprocess functions'])) {
+        $incomplete_previous_hook = $cache[$previous_hook];
+        unset($incomplete_previous_hook['incomplete preprocess functions']);
+      }
+      $previous_hook = substr($previous_hook, 0, $pos);
+
+      // If base hook exists clone of it for the preprocess function
+      // without a template.
+      // @see https://www.drupal.org/node/2457295
+      if (isset($cache[$previous_hook]) && !isset($cache[$previous_hook]['incomplete preprocess functions'])) {
+        $cache[$hook] = $incomplete_previous_hook + $cache[$previous_hook];
+        if (isset($incomplete_previous_hook['preprocess functions'])) {
+          $diff = array_diff($incomplete_previous_hook['preprocess functions'], $cache[$previous_hook]['preprocess functions']);
+          $cache[$hook]['preprocess functions'] = array_merge($cache[$previous_hook]['preprocess functions'], $diff);
+        }
+        // If a base hook isn't set, this is the actual base hook.
+        if (!isset($cache[$previous_hook]['base hook'])) {
+          $cache[$hook]['base hook'] = $previous_hook;
+        }
+      }
+      return $hook;
+    }
+  }
+
+  /**
    * Completes the theme registry adding discovered functions and hooks.
    *
    * @param array $cache
@@ -642,21 +679,8 @@ protected function postProcessExtension(array &$cache, ActiveTheme $theme) {
           // Process non-existing hook and register it.
           // Look for a previously defined hook that is either a less specific
           // suggestion hook or the base hook.
-          $previous_hook = $hook;
-          while (!isset($cache[$previous_hook]) && $pos = strrpos($previous_hook, '__')) {
-            $previous_hook = substr($previous_hook, 0, $pos);
-            // If base hook exists clone of it for the preprocess function
-            // without a template.
-            // @see https://www.drupal.org/node/2457295
-            if (isset($cache[$previous_hook])) {
-              $cache[$hook] = $cache[$previous_hook];
-              // If a base hook isn't set, this is the actual base hook.
-              if (!isset($cache[$previous_hook]['base hook'])) {
-                $cache[$hook]['base hook'] = $previous_hook;
-              }
-              $cache[$hook]['preprocess functions'][] = $preprocessor;
-            }
-          }
+          $hook = $this->completeSuggestion($hook, $cache);
+          $cache[$hook]['preprocess functions'][] = $preprocessor;
         }
       }
     }
@@ -667,9 +691,9 @@ protected function postProcessExtension(array &$cache, ActiveTheme $theme) {
       // The 'base hook' is only applied to derivative hooks already registered
       // from a pattern. This is typically set from
       // drupal_find_theme_functions() and drupal_find_theme_templates().
-      if (isset($info['base hook']) && isset($cache[$info['base hook']]['preprocess functions'])) {
-        $diff = array_diff($info['preprocess functions'], $cache[$info['base hook']]['preprocess functions']);
-        $cache[$hook]['preprocess functions'] = array_merge($cache[$info['base hook']]['preprocess functions'], $diff);
+      if (isset($info['incomplete preprocess functions'])) {
+        $hook = $this->completeSuggestion($hook, $cache);
+        unset($cache[$hook]['incomplete preprocess functions']);
       }
 
       // Optimize the registry.