diff --git a/lib/driver.js b/lib/driver.js
index <HASH>..<HASH> 100644
--- a/lib/driver.js
+++ b/lib/driver.js
@@ -206,7 +206,7 @@ class IosDriver extends BaseDriver {
 
       // if we have an ipa file, set it in opts
       if (this.opts.app) {
-        let ext = this.opts.app.substring(this.opts.app.length - 4).toLowerCase();
+        let ext = this.opts.app.substring(this.opts.app.length - 3).toLowerCase();
         if (ext === 'ipa') {
           this.opts.ipa = this.opts.app;
         }
fix set in opts ipa file

fix incorrect substring