diff --git a/src/js/messaging.js b/src/js/messaging.js
index 05b9ce9ea..98fd3534c 100644
--- a/src/js/messaging.js
+++ b/src/js/messaging.js
@@ -980,7 +980,7 @@ var backupUserData = function(callback) {
             timeStamp: Date.now(),
             version: vAPI.app.version,
             userSettings: µb.userSettings,
-            filterLists: µb.remoteBlacklists,
+            filterLists: µb.extractSelectedFilterLists(),
             netWhitelist: µb.stringFromWhitelist(µb.netWhitelist),
             dynamicFilteringString: µb.permanentFirewall.toString(),
             hostnameSwitchesString: µb.hnSwitches.toString(),
diff --git a/src/js/storage.js b/src/js/storage.js
index 8854fe9a0..66ec14390 100644
--- a/src/js/storage.js
+++ b/src/js/storage.js
@@ -91,6 +91,26 @@
 
 /******************************************************************************/
 
+// This will remove all unused filter list entries from
+// µBlock.remoteBlacklists`. This helps reduce the size of backup files.
+
+µBlock.extractSelectedFilterLists = function() {
+    var r = JSON.parse(JSON.stringify(this.remoteBlacklists));
+
+    for ( var path in r ) {
+        if ( r.hasOwnProperty(path) === false ) {
+            continue;
+        }
+        if ( r[path].off !== false ) {
+            delete r[path];
+        }
+    }
+
+    return r;
+};
+
+/******************************************************************************/
+
 µBlock.saveUserFilters = function(content, callback) {
     return this.assets.put(this.userFiltersPath, content, callback);
 };