diff --git a/mollom.admin.inc b/mollom.admin.inc
index 091ba0b..cc106f2 100644
--- a/mollom.admin.inc
+++ b/mollom.admin.inc
@@ -26,27 +26,24 @@ function mollom_admin_form_list() {
   );
   $result = db_query("SELECT form_id FROM {mollom_form}");
   $forms = array();
-  $modules = array();
+  $module_info = array();
   while ($form_id = db_result($result)) {
     $forms[$form_id] = mollom_form_load($form_id);
-
     // Load module information.
     $module = $forms[$form_id]['module'];
-    if (!isset($modules[$module])) {
+    if (!isset($module_info[$module])) {
       // Default to the module's machine name in case the query below does not
       // lead to a result (which is possible, because D6 does not inform modules
       // about uninstalled modules).
-      $modules[$module] = $module;
-      $module_info = db_result(db_query("SELECT info FROM {system} WHERE type = 'module' AND name = '%s'", $module));
-      if ($module_info) {
-        $module_info = unserialize($module_info);
-        $modules[$module] = t($module_info['name']);
+      $module_info[$module]['name'] = $module;
+      $system_info = db_result(db_query("SELECT info FROM {system} WHERE type = 'module' AND name = '%s'", $module));
+      if ($system_info) {
+        $module_info[$module] = unserialize($system_info);
       }
     }
-
     $forms[$form_id]['title'] = t('!module: !form-title', array(
       '!form-title' => $forms[$form_id]['title'],
-      '!module' => $modules[$module],
+      '!module' => t($module_info[$module]['name']),
     ));
   }
 
@@ -55,21 +52,38 @@ function mollom_admin_form_list() {
 
   $rows = array();
   foreach ($forms as $form_id => $mollom_form) {
+    $row_attributes = array();
     $row = array();
     $row[] = $mollom_form['title'];
-    if ($mollom_form['mode'] == MOLLOM_MODE_ANALYSIS) {
-      // @todo Output unsure mode in summary listing.
-      $row[] = t('!protection-mode (@discard)', array(
-        '!protection-mode' => $modes[$mollom_form['mode']],
-        '@discard' => $mollom_form['discard'] ? t('discard') : t('retain'),
-      ));
+    if (isset($modes[$mollom_form['mode']])) {
+      if ($mollom_form['mode'] == MOLLOM_MODE_ANALYSIS) {
+        // @todo Output unsure mode in summary listing.
+        $row[] = t('!protection-mode (@discard)', array(
+          '!protection-mode' => $modes[$mollom_form['mode']],
+          '@discard' => $mollom_form['discard'] ? t('discard') : t('retain'),
+        ));
+      }
+      else {
+        $row[] = $modes[$mollom_form['mode']];
+      }
+    }
+    else {
+      $row[] = t('- orphan -');
+    }
+    if (empty($mollom_form['orphan'])) {
+      $row[] = l(t('Configure'), 'admin/settings/mollom/manage/' . $form_id);
     }
     else {
-      $row[] = $modes[$mollom_form['mode']];
+      $row[] = '';
+      $row_attributes['class'] = 'error';
+      drupal_set_message(t("%module module's %form_id form no longer exists.", array(
+        '%form_id' => $form_id,
+        '%module' => isset($module_info[$mollom_form['module']]['name']) ? t($module_info[$mollom_form['module']]['name']) : $mollom_form['module'],
+      )), 'warning');
     }
-    $row[] = l(t('Configure'), 'admin/settings/mollom/manage/' . $form_id);
     $row[] = l(t('Unprotect'), 'admin/settings/mollom/unprotect/' . $form_id);
-    $rows[] = $row;
+
+    $rows[] = $row_attributes + array('data' => $row);
   }
 
   // Add a row to add a form.
diff --git a/mollom.module b/mollom.module
index be1c7d7..23a1c2c 100644
--- a/mollom.module
+++ b/mollom.module
@@ -880,15 +880,13 @@ function mollom_form_list() {
  *   The form id to return information for.
  * @param $module
  *   The module name $form_id belongs to.
+ * @param array $form_list
+ *   (optional) The return value of hook_mollom_form_list() of $module, if
+ *   already kown. Primarily used by mollom_form_load().
  */
-function mollom_form_info($form_id, $module) {
-  $form_info = module_invoke($module, 'mollom_form_info', $form_id);
-  if (empty($form_info)) {
-    $form_info = array();
-  }
-
-  // Ensure default properties.
-  $form_info += array(
+function mollom_form_info($form_id, $module, $form_list = NULL) {
+  // Default properties.
+  $form_info = array(
     // Base properties.
     'form_id' => $form_id,
     'title' => $form_id,
@@ -907,8 +905,31 @@ function mollom_form_info($form_id, $module) {
     'elements' => array(),
     'mapping' => array(),
     'mail ids' => array(),
+    'orphan' => TRUE,
   );
 
+  // Fetch the basic form information from hook_mollom_form_list() first.
+  // This makes the integrating module (needlessly) rebuild all of its available
+  // forms, but the base properties are absolutely required here, so we can
+  // apply the default properties below.
+  if (!isset($form_list)) {
+    $form_list = module_invoke($module, 'mollom_form_list');
+  }
+  // If it is not listed, then the form has vanished.
+  if (!isset($form_list[$form_id])) {
+    return $form_info;
+  }
+  $module_form_info = module_invoke($module, 'mollom_form_info', $form_id);
+  // If no form info exists, then the form has vanished.
+  if (!isset($module_form_info)) {
+    return $form_info;
+  }
+  unset($form_info['orphan']);
+
+  // Any information in hook_mollom_form_info() overrides the list info.
+  $form_info = array_merge($form_info, $form_list[$form_id]);
+  $form_info = array_merge($form_info, $module_form_info);
+
   // Allow modules to alter the default form information.
   drupal_alter('mollom_form_info', $form_info, $form_id);
 
@@ -927,7 +948,7 @@ function mollom_form_new($form_id) {
   if (isset($form_list[$form_id])) {
     $mollom_form += $form_list[$form_id];
   }
-  $mollom_form += mollom_form_info($form_id, $form_list[$form_id]['module']);
+  $mollom_form += mollom_form_info($form_id, $form_list[$form_id]['module'], $form_list);
 
   // Enable all fields for textual analysis by default.
   $mollom_form['checks'] = array('spam');
@@ -951,11 +972,9 @@ function mollom_form_load($form_id) {
       $mollom_form['enabled_fields'] = unserialize($mollom_form['enabled_fields']);
 
       // Attach form registry information.
-      $form_list = module_invoke($mollom_form['module'], 'mollom_form_list');
-      if (isset($form_list[$form_id])) {
-        $mollom_form += $form_list[$form_id];
-      }
-      $mollom_form += mollom_form_info($form_id, $mollom_form['module']);
+      $form_info = mollom_form_info($form_id, $mollom_form['module']);
+      $mollom_form += $form_info;
+
 
       cache_set($cid, $mollom_form);
     }
@@ -3380,7 +3399,9 @@ function node_mollom_form_info($form_id) {
   // Retrieve internal type from $form_id.
   $nodetype = drupal_substr($form_id, 0, -10);
 
-  $type = node_get_types('type', $nodetype);
+  if (!$type = node_get_types('type', $nodetype)) {
+    return;
+  }
   $form_info = array(
     // @todo This is incompatible with node access.
     'bypass access' => array('administer nodes'),
diff --git a/tests/mollom.test b/tests/mollom.test
index deec455..4fc98af 100644
--- a/tests/mollom.test
+++ b/tests/mollom.test
@@ -2587,6 +2587,40 @@ class MollomFormConfigurationTestCase extends MollomWebTestCase {
   }
 
   /**
+   * Tests invalid (stale) form configurations.
+   */
+  function testInvalidForms() {
+    $forms = array(
+      'nonexisting' => 'nonexisting_form',
+      'user' => 'user_nonexisting_form',
+      'node' => 'nonexisting_node_form',
+      'comment' => 'comment_node_nonexisting_form',
+    );
+    $mode = 0;
+    foreach ($forms as $module => $form_id) {
+      $mollom_form = mollom_form_info($form_id, $module, array());
+      $mollom_form['mode'] = $mode++;
+      mollom_form_save($mollom_form);
+    }
+
+    // Just visiting the form administration page is sufficient; it will throw
+    // fatal errors, warnings, and notices.
+    $this->drupalLogin($this->admin_user);
+    $this->drupalGet('admin/settings/mollom');
+
+    // Ensure that unprotecting the forms does not throw any notices either.
+    foreach ($forms as $form_id) {
+      $this->assertNoLinkByHref('admin/settings/mollom/manage/' . $form_id);
+      $this->assertLinkByHref('admin/settings/mollom/unprotect/' . $form_id);
+      $this->drupalPost('admin/settings/mollom/unprotect/' . $form_id, array(), t('Confirm'));
+      $this->assertNoLinkByHref('admin/settings/mollom/unprotect/' . $form_id);
+    }
+    // Confirm deletion.
+    $count = db_result(db_query('SELECT 1 FROM {mollom_form}'));
+    $this->assertFalse($count, 'No forms found.');
+  }
+
+  /**
    * Tests programmatically, conditionally disabling Mollom.
    */
   function testFormAlter() {