diff --git a/index.js b/index.js
index 7c52a4c..cfae79c 100644
--- a/index.js
+++ b/index.js
@@ -45,9 +45,11 @@ class ServerlessPlugin {
         if (!fs.existsSync(pathToCoffee))
           pathToCoffee = 'coffee'
         const result = spawnSync(pathToCoffee, args, options);
-        const sterr = result.stderr.toString();
-        if (sterr) {
-          reject(sterr);
+        if (result.stderr) {
+          const sterr = result.stderr.toString();
+          if (sterr) {
+            reject(sterr);
+          }
         }
 
         // zip