diff --git a/main/astrodatadownloader/astrodatadownloader.py b/main/astrodatadownloader/astrodatadownloader.py
index 6fe090b..e8c9a75 100644
--- a/main/astrodatadownloader/astrodatadownloader.py
+++ b/main/astrodatadownloader/astrodatadownloader.py
@@ -78,9 +78,9 @@ def fitsFilenameFilterFunc(table, key_colnames):
     return False
 
 def downloadStarProducts(obs_wanted, keplerCadences, k2Cadences):
-    if(len(keplerCadences) is not 2):
+    if(len(keplerCadences) != 2):
         raise Exception("keplerCadences needs to have length 2")
-    if(len(k2Cadences) is not 2):
+    if(len(k2Cadences) != 2):
         raise Exception("k2Cadences need to have length 2")
 
     dataProducts = Observations.get_product_list(obs_wanted)