diff --git a/humbug/settings.py b/humbug/settings.py
index e1fa786948..a5e7944579 100644
--- a/humbug/settings.py
+++ b/humbug/settings.py
@@ -7,6 +7,9 @@ deployed = (platform.node() == 'humbug-dev')
 DEBUG = not deployed
 TEMPLATE_DEBUG = DEBUG
 
+if DEBUG:
+    INTERNAL_IPS = ('127.0.0.1',)
+
 ADMINS = (
     ('Jessica McKellar', 'jessica.mckellar@gmail.com'),
 )
diff --git a/templates/zephyr/index.html b/templates/zephyr/index.html
index 2f7a7ea4a3..c82309cd21 100644
--- a/templates/zephyr/index.html
+++ b/templates/zephyr/index.html
@@ -29,6 +29,11 @@
 <script type="text/javascript" src="/static/third/jquery/jquery.form.js"></script>
 <script type="text/javascript" src="/static/third/ich/ICanHaz.min.js"></script>
 <script type="text/javascript" src="/static/js/zephyr.js"></script>
+
+{% if debug %}
+<script type="text/javascript" src="/static/js/debug.js"></script>
+{% endif %}
+
 <script type="text/javascript">
 var initial_zephyr_array = {{ zephyr_array }};
 var initial_pointer = {{ user_profile.pointer }};
diff --git a/zephyr/static/js/debug.js b/zephyr/static/js/debug.js
new file mode 100644
index 0000000000..255183c1ba
--- /dev/null
+++ b/zephyr/static/js/debug.js
@@ -0,0 +1,24 @@
+/* WARNING:
+
+    This file is only included when Django's DEBUG = True and your
+    host is in INTERNAL_IPS.
+
+    Do not commit any code to zephyr.js which uses these functions.
+    They are for debugging use only.
+
+    The file may still be accessible under other circumstances, so do
+    not put sensitive information here. */
+
+/*
+      print_elapsed_time("foo", foo)
+
+    evaluates to foo() and prints the elapsed time
+    to the console along with the name "foo". */
+
+function print_elapsed_time(name, fun) {
+    var t0 = new Date().getTime();
+    var out = fun();
+    var t1 = new Date().getTime();
+    console.log(name + ': ' + (t1 - t0) + ' ms');
+    return out;
+}