diff --git a/umbra/behaviors.d/facebook.js b/umbra/behaviors.d/facebook.js
index 12e57d0..385af7f 100644
--- a/umbra/behaviors.d/facebook.js
+++ b/umbra/behaviors.d/facebook.js
@@ -1,4 +1,5 @@
-//.*facebook.com.* 
+//^https?://(?:www\.)?facebook.com/.*$
+
 var isOnScreen = function(e) {
         var eTop = e.getBoundingClientRect().top;
         return eTop > window.scrollY && eTop < window.scrollY + window.innerHeight;
diff --git a/umbra/behaviors.d/flickr.js b/umbra/behaviors.d/flickr.js
index 8cddfd6..c5b6707 100644
--- a/umbra/behaviors.d/flickr.js
+++ b/umbra/behaviors.d/flickr.js
@@ -1,4 +1,5 @@
-//.*flickr.com.*
+//^https?://(?:www\.)?flickr.com/.*$
+
 setInterval(function() { window.scrollBy(0,50); }, 100);
 
 setTimeout(function() {