diff --git a/profile_privacy.install b/profile_privacy.install
index 14f3212..4f685bf 100644
--- a/profile_privacy.install
+++ b/profile_privacy.install
@@ -27,11 +27,13 @@ function profile_privacy_schema() {
       'fid' => array(
         'type' => 'int',
         'unsigned' => TRUE,
+        'not null' => TRUE,
         'default' => 0,
       ),
       'uid' => array(
         'type' => 'int',
         'unsigned' => TRUE,
+        'not null' => TRUE,
         'default' => 0,
       ),
       'private' => array(
@@ -63,3 +65,34 @@ function profile_privacy_install() {
 function profile_privacy_uninstall() {
   drupal_uninstall_schema('profile_privacy');
 }
+
+/**
+ * Implementation of hook_update_N().
+ */
+function profile_privacy_update_6100(&$sandbox) {
+  $return = array();
+
+  // Modifies the profile_privacy_fields.fid field.
+  db_drop_primary_key($return, 'profile_privacy_fields');
+  db_change_field($return, 'profile_privacy_fields', 'fid', 'fid',
+    array('type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0),
+    array('primary key' => array('fid'))
+  );
+
+  // Modifies the profile_privacy_values.fid field.
+  db_drop_index($return, 'profile_privacy_values', 'fid');
+  db_change_field($return, 'profile_privacy_values', 'fid', 'fid',
+    array('type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0),
+    array('indexes' => array('fid' => array('fid')))
+  );
+
+  // Modifies the profile_privacy_values.uid field.
+  db_drop_index($return, 'profile_privacy_values', 'uid');
+  db_change_field($return, 'profile_privacy_values', 'uid', 'uid',
+    array('type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0),
+    array('indexes' => array('uid' => array('uid')))
+  );
+
+  return $return;
+}
+