diff --git a/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp b/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
index 39f9cf4fd49f..9e544bec33d1 100644
--- a/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
+++ b/toolkit/components/url-classifier/nsUrlClassifierDBService.cpp
@@ -1204,25 +1204,6 @@ nsUrlClassifierDBService::Init()
     CONFIRM_AGE_DEFAULT_SEC);
   ReadTablesFromPrefs();
 
-  // Do we *really* need to be able to change all of these at runtime?
-  Preferences::AddStrongObserver(this, CHECK_MALWARE_PREF);
-  Preferences::AddStrongObserver(this, CHECK_PHISHING_PREF);
-  Preferences::AddStrongObserver(this, CHECK_TRACKING_PREF);
-  Preferences::AddStrongObserver(this, CHECK_TRACKING_PB_PREF);
-  Preferences::AddStrongObserver(this, CHECK_FORBIDDEN_PREF);
-  Preferences::AddStrongObserver(this, CHECK_BLOCKED_PREF);
-  Preferences::AddStrongObserver(this, GETHASH_NOISE_PREF);
-  Preferences::AddStrongObserver(this, CONFIRM_AGE_PREF);
-  Preferences::AddStrongObserver(this, PHISH_TABLE_PREF);
-  Preferences::AddStrongObserver(this, MALWARE_TABLE_PREF);
-  Preferences::AddStrongObserver(this, TRACKING_TABLE_PREF);
-  Preferences::AddStrongObserver(this, TRACKING_WHITELIST_TABLE_PREF);
-  Preferences::AddStrongObserver(this, FORBIDDEN_TABLE_PREF);
-  Preferences::AddStrongObserver(this, BLOCKED_TABLE_PREF);
-  Preferences::AddStrongObserver(this, DOWNLOAD_BLOCK_TABLE_PREF);
-  Preferences::AddStrongObserver(this, DOWNLOAD_ALLOW_TABLE_PREF);
-  Preferences::AddStrongObserver(this, DISALLOW_COMPLETION_TABLE_PREF);
-
   // Force PSM loading on main thread
   nsresult rv;
   nsCOMPtr<nsICryptoHash> dummy = do_CreateInstance(NS_CRYPTO_HASH_CONTRACTID, &rv);
@@ -1271,6 +1252,28 @@ nsUrlClassifierDBService::Init()
   observerService->AddObserver(this, "profile-before-change", false);
   observerService->AddObserver(this, "xpcom-shutdown-threads", false);
 
+  // XXX: Do we *really* need to be able to change all of these at runtime?
+  // Note: These observers should only be added when everything else above has
+  //       succeeded. Failing to do so can cause long shutdown times in certain
+  //       situations. See Bug 1247798 and Bug 1244803.
+  Preferences::AddStrongObserver(this, CHECK_MALWARE_PREF);
+  Preferences::AddStrongObserver(this, CHECK_PHISHING_PREF);
+  Preferences::AddStrongObserver(this, CHECK_TRACKING_PREF);
+  Preferences::AddStrongObserver(this, CHECK_TRACKING_PB_PREF);
+  Preferences::AddStrongObserver(this, CHECK_FORBIDDEN_PREF);
+  Preferences::AddStrongObserver(this, CHECK_BLOCKED_PREF);
+  Preferences::AddStrongObserver(this, GETHASH_NOISE_PREF);
+  Preferences::AddStrongObserver(this, CONFIRM_AGE_PREF);
+  Preferences::AddStrongObserver(this, PHISH_TABLE_PREF);
+  Preferences::AddStrongObserver(this, MALWARE_TABLE_PREF);
+  Preferences::AddStrongObserver(this, TRACKING_TABLE_PREF);
+  Preferences::AddStrongObserver(this, TRACKING_WHITELIST_TABLE_PREF);
+  Preferences::AddStrongObserver(this, FORBIDDEN_TABLE_PREF);
+  Preferences::AddStrongObserver(this, BLOCKED_TABLE_PREF);
+  Preferences::AddStrongObserver(this, DOWNLOAD_BLOCK_TABLE_PREF);
+  Preferences::AddStrongObserver(this, DOWNLOAD_ALLOW_TABLE_PREF);
+  Preferences::AddStrongObserver(this, DISALLOW_COMPLETION_TABLE_PREF);
+
   return NS_OK;
 }