diff --git a/lib/caching.js b/lib/caching.js
index 6cb1841..7c35836 100644
--- a/lib/caching.js
+++ b/lib/caching.js
@@ -1,6 +1,7 @@
 /*jshint maxcomplexity:15*/
 /*jshint -W072 */
 var domain = require('domain');
+var CallbackFiller = require('./callback_filler');
 
 var caching = function(args) {
     args = args || {};
@@ -21,7 +22,7 @@ var caching = function(args) {
     // do we handle a cache error the same as a cache miss?
     self.ignoreCacheErrors = args.ignoreCacheErrors || false;
 
-    self.queues = {};
+    var callbackFiller = new CallbackFiller();
 
     /**
      * Wraps a function in cache. I.e., the first time the function is run,
@@ -43,44 +44,34 @@ var caching = function(args) {
             options = undefined;
         }
 
-        if (self.queues[key]) {
-            self.queues[key].push({cb: cb, domain: process.domain});
+        if (callbackFiller.queues[key]) {
+            callbackFiller.queues[key].push({cb: cb, domain: process.domain});
             return;
         }
 
-        self.queues[key] = [{cb: cb, domain: process.domain}];
-
-        function fillCallbacks(err, data) {
-            var waiting = self.queues[key];
-            delete self.queues[key];
-
-            waiting.forEach(function(task) {
-                var taskDomain = task.domain || domain.create();
-                taskDomain.bind(task.cb)(err, data);
-            });
-        }
+        callbackFiller.queues[key] = [{cb: cb, domain: process.domain}];
 
         self.store.get(key, options, function(err, result) {
             if (err && (!self.ignoreCacheErrors)) {
-                fillCallbacks(err);
+                callbackFiller.fill(key, err);
             } else if (result) {
-                fillCallbacks(null, result);
+                callbackFiller.fill(key, null, result);
             } else {
                 domain
                 .create()
                 .on('error', function(err) {
-                    fillCallbacks(err);
+                    callbackFiller.fill(key, err);
                 })
                 .bind(work)(function(err, data) {
                     if (err) {
-                        fillCallbacks(err);
+                        callbackFiller.fill(key, err);
                         return;
                     }
                     self.store.set(key, data, options, function(err) {
                         if (err && (!self.ignoreCacheErrors)) {
-                            fillCallbacks(err);
+                            callbackFiller.fill(key, err);
                         } else {
-                            fillCallbacks(null, data);
+                            callbackFiller.fill(key, null, data);
                         }
                     });
                 });
diff --git a/lib/callback_filler.js b/lib/callback_filler.js
new file mode 100644
index 0000000..163aa7e
--- /dev/null
+++ b/lib/callback_filler.js
@@ -0,0 +1,19 @@
+var domain = require('domain');
+
+function CallbackFiller() {
+    this.queues = {};
+}
+
+CallbackFiller.prototype.fill = function(key, err, data) {
+    var self = this;
+
+    var waiting = self.queues[key];
+    delete self.queues[key];
+
+    waiting.forEach(function(task) {
+        var taskDomain = task.domain || domain.create();
+        taskDomain.bind(task.cb)(err, data);
+    });
+};
+
+module.exports = CallbackFiller;
diff --git a/lib/multi_caching.js b/lib/multi_caching.js
index 18bfe5e..72d67df 100644
--- a/lib/multi_caching.js
+++ b/lib/multi_caching.js
@@ -1,5 +1,6 @@
 var async = require('async');
 var domain = require('domain');
+var CallbackFiller = require('./callback_filler');
 
 /**
  * Module that lets you specify a hierarchy of caches.
@@ -10,7 +11,7 @@ var multi_caching = function(caches) {
         throw new Error('multi_caching requires an array of caches');
     }
 
-    self.queues = {};
+    var callbackFiller = new CallbackFiller();
 
     function get_from_highest_priority_cache(key, options, cb) {
         if (typeof options === 'function') {
@@ -88,26 +89,16 @@ var multi_caching = function(caches) {
             options = undefined;
         }
 
-        if (self.queues[key]) {
-            self.queues[key].push({cb: cb, domain: process.domain});
+        if (callbackFiller.queues[key]) {
+            callbackFiller.queues[key].push({cb: cb, domain: process.domain});
             return;
         }
 
-        self.queues[key] = [{cb: cb, domain: process.domain}];
-
-        function fillCallbacks(err, data) {
-            var waiting = self.queues[key];
-            delete self.queues[key];
-
-            waiting.forEach(function(task) {
-                var taskDomain = task.domain || domain.create();
-                taskDomain.bind(task.cb)(err, data);
-            });
-        }
+        callbackFiller.queues[key] = [{cb: cb, domain: process.domain}];
 
         get_from_highest_priority_cache(key, function(err, result, index) {
             if (err) {
-                return fillCallbacks(err);
+                return callbackFiller.fill(key, err);
             } else if (result) {
                 var caches_to_update = caches.slice(0, index);
                 var opts = {
@@ -121,17 +112,17 @@ var multi_caching = function(caches) {
                 }
 
                 set_in_multiple_caches(caches_to_update, opts, function(err) {
-                    fillCallbacks(err, result);
+                    callbackFiller.fill(key, err, result);
                 });
             } else {
                 domain
                     .create()
                     .on('error', function(err) {
-                        fillCallbacks(err);
+                        callbackFiller.fill(key, err);
                     })
                     .bind(work)(function(err, data) {
                     if (err) {
-                        fillCallbacks(err);
+                        callbackFiller.fill(key, err);
                         return;
                     }
                     var opts = {
@@ -145,9 +136,9 @@ var multi_caching = function(caches) {
                     }
                     set_in_multiple_caches(caches, opts, function(err) {
                         if (err) {
-                            fillCallbacks(err);
+                            callbackFiller.fill(key, err);
                         } else {
-                            fillCallbacks(null, data);
+                            callbackFiller.fill(key, null, data);
                         }
                     });
                 });