Index: fb.module
===================================================================
--- fb.module	(revision 3785)
+++ fb.module	(working copy)
@@ -356,6 +356,16 @@
       return NULL;
     }

+    if (Facebook::VERSION >= "3") {
+      $message = 'This version of modules/fb is compatible with Facebook PHP SDK version 2.x, but %version was found.  Either upgrade modules/fb or downgrade %fb_platform.';
+      $args = array('%fb_platform' => $fb_platform, '%version' => Facebook::VERSION);
+      if (user_access('access administration pages')) {
+        drupal_set_message(t($message, $args));
+      }
+      watchdog('fb', $message, $args, WATCHDOG_ERROR);
+      return NULL;
+    }
+
     // We don't have a cached resource for this app, so we're going to create one.
     $fb = new Facebook(array(
                          'appId' => $fb_app->id,
Index: fb.install
===================================================================
--- fb.install	(revision 3785)
+++ fb.install	(working copy)
@@ -62,9 +62,15 @@
   $fb_platform = variable_get(FB_VAR_API_FILE, $fb_lib_path . '/src/facebook.php');

   if (class_exists('Facebook')) {
-    $status['description'] = $t('Facebook PHP SDK loaded.');
-    $status['severity'] = REQUIREMENT_OK;
-    $status['value'] = $t('Loaded');
+    $status['value'] = Facebook::VERSION;
+    if (Facebook::VERSION >= "3") {
+      $status['description'] = $t('Expected version 2.x.y of Facebook PHP SDK.');
+      $status['severity'] = REQUIREMENT_ERROR;
+    }
+    else {
+      $status['description'] = $t('Facebook PHP SDK loaded.');
+      $status['severity'] = REQUIREMENT_OK;
+    }
   }
   elseif (include($fb_platform)) { // include() better than file_exists().
     $status['description'] = $t('Facebook SDK found at %path',