diff --git a/lib/cloudcmd.js b/lib/cloudcmd.js
index 45eaaba5..d7a8ebc5 100644
--- a/lib/cloudcmd.js
+++ b/lib/cloudcmd.js
@@ -74,7 +74,7 @@
                 value = createPass(config('algo'), value);
                 break;
             case 'prefix':
-                if (value) {
+                if (typeof value === 'string') {
                     if (!~value.indexOf('/'))
                         value = '/' + value;
                     else if (value.length === 1)