diff --git a/src/pygenstability/constructors.py b/src/pygenstability/constructors.py
index 2219466..794b070 100644
--- a/src/pygenstability/constructors.py
+++ b/src/pygenstability/constructors.py
@@ -4,7 +4,7 @@
 
 .. math::
 
-    Q_{gen}(t,H) = \mathrm{Tr} \left [H^T \left (F(t)-\sum_{k=1}^m v_{2k} v_{2k+1}^T\right)H\right]
+    Q_{gen}(t,H) = \mathrm{Tr} \left [H^T \left (F(t)-\sum_{k=1}^m v_{2k-1} v_{2k}^T\right)H\right]
 
 where :math:`F(t)` is the quality matrix and :math:`v_k` are null model vectors.
 
diff --git a/src/pygenstability/pygenstability.py b/src/pygenstability/pygenstability.py
index bc4c093..d672ea0 100644
--- a/src/pygenstability/pygenstability.py
+++ b/src/pygenstability/pygenstability.py
@@ -4,7 +4,7 @@
 
 .. math::
 
-    Q_{gen}(t,H) = \mathrm{Tr} \left [H^T \left (F(t)-\sum_{k=0}^m v_{2k} v_{2k+1}^T\right)H\right]
+    Q_{gen}(t,H) = \mathrm{Tr} \left [H^T \left (F(t)-\sum_{k=1}^m v_{2k-1} v_{2k}^T\right)H\right]
 
 where :math:`F(t)` is the quality matrix and :math:`v_k` are null model vectors.
 The choice of the quality matrix and null model vectors are arbitrary in the generalized