diff --git a/updater/src/index.js b/updater/src/index.js
index 0efdc8e..f7dcd57 100644
--- a/updater/src/index.js
+++ b/updater/src/index.js
@@ -15,7 +15,7 @@ function spawnAsync(file, args, opts = {}) {
     child.on('error', reject)
     child.on('close', code => {
       if (code === 0) resolve({ stdout, stderr })
-      else reject(new Error(`Exit ${code}: ${stderr.slice(-500)}`))
+      else reject(new Error(`Exit ${code}: ${(stderr + stdout).slice(-500)}`))
     })
     if (opts.timeout) {
       setTimeout(() => { child.kill(); reject(new Error('Timeout')) }, opts.timeout)