diff --git a/lib/repl.js b/lib/repl.js
index d5b55f2027..4d144f17cd 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -256,7 +256,7 @@ REPLServer.prototype.complete = function(line) {
       // Kind of lame that this needs to be updated manually.
       // Intentionally excluding moved modules: posix, utils.
       var builtinLibs = ['assert', 'buffer', 'child_process', 'crypto', 'dgram',
-        'dns', 'events', 'file', 'freelist', 'fs', 'http', 'net', 'path',
+        'dns', 'events', 'file', 'freelist', 'fs', 'http', 'net', 'os', 'path',
         'querystring', 'readline', 'repl', 'string_decoder', 'util', 'tcp',
         'url'];
       completionGroups.push(builtinLibs);