diff --git a/script/lib/omaha.py b/script/lib/omaha.py
index 2c25f21eaf79..32954dddb76c 100644
--- a/script/lib/omaha.py
+++ b/script/lib/omaha.py
@@ -71,11 +71,11 @@ def get_base64_authorization(omahaid, omahapw):
 
 # To-Do: Add functions to create apps
 def get_appguid(channel, platform):
-    if channel in 'dev' or channel in 'release' and platform in 'darwin':
+    if channel in ['dev'] or platform in ['darwin'] and channel in ['beta', 'dev', 'release']:
         return '{CB2150F2-595F-4633-891A-E39720CE0531}'
-    elif channel in 'beta':
+    elif channel in ['beta']:
         return '{103BD053-949B-43A8-9120-2E424887DE11}'
-    elif channel in 'release':
+    elif channel in ['release']:
         return '{AFE6A462-C574-4B8A-AF43-4CC60DF4563B}'