diff --git a/packages/xen-api/src/index.js b/packages/xen-api/src/index.js
index 03991d165..831e85d12 100644
--- a/packages/xen-api/src/index.js
+++ b/packages/xen-api/src/index.js
@@ -145,7 +145,7 @@ const isReadOnlyCall = (method, args) => (
 //
 // - cast integers to strings
 const prepareParam = param => {
-  if (isInteger(param === 'number')) {
+  if (isInteger(param)) {
     return String(param)
   }