diff --git a/browser/build.js b/browser/build.js
index 545219f..865324a 100644
--- a/browser/build.js
+++ b/browser/build.js
@@ -63,7 +63,7 @@ var createBitcore = function(opts) {
   opts.dir = opts.dir || '';
 
   // concat browser vendor files
-  exec('cd ' + opts.dir + 'browser; sh concat.sh', puts);
+  exec('cd ' + opts.dir + 'browser & sh concat.sh', puts);
 
   if (!opts.includeall && (!opts.submodules || opts.submodules.length === 0)) {
     if (!opts.stdout) console.log('Must use either -s or -a option. For more info use the --help option');