diff --git a/analytics/utils/__init__.py b/analytics/utils/__init__.py
index bb20e6c..9f32eeb 100644
--- a/analytics/utils/__init__.py
+++ b/analytics/utils/__init__.py
@@ -212,7 +212,7 @@ def ar_mean(numbers):
 
 def get_av_model(patterns_list):
     x = len(patterns_list[0])
-    if len(patterns_list[1]) != x:
+    if len(pattern_list) > 1 and len(patterns_list[1]) != x:
         raise NameError('All elements of patterns_list should have same length')
     model_pat = []
     for i in range(x):