diff --git a/measures/rankedlist/RBO.py b/measures/rankedlist/RBO.py
index 33ef23f..41b0fd5 100644
--- a/measures/rankedlist/RBO.py
+++ b/measures/rankedlist/RBO.py
@@ -49,7 +49,7 @@ def score(l1, l2, p = 0.98):
     sum2 = 0.0
     for i in range(l-s):
         d = s+i+1
-        sum2 += x_d[d]*(d-s)/(d*s)*pow(p,d)
+        sum2 += x_d[s]*(d-s)/(d*s)*pow(p,d)
 
     sum3 = ((x_d[l]-x_d[s])/l+x_d[s]/s)*pow(p,l)
 
@@ -61,8 +61,8 @@ def score(l1, l2, p = 0.98):
 if __name__ == "__main__":
     list1 = ['0','1','2','3','4','5']
     list2 = ['1','0','2','3','4','5']
-    print RBO(list1,list2, p = 0.98)
+    print score(list1,list2, p = 0.98)
 
     list1 = ['012']
     list2 = []
-    print RBO(list1, list2, p = 0.98)
+    print score(list1, list2, p = 0.98)