diff --git a/aabbtree.py b/aabbtree.py
index 80b1a54..b1563ed 100644
--- a/aabbtree.py
+++ b/aabbtree.py
@@ -108,7 +108,6 @@ def perimeter(self):
         :math:`l_1, ..., l_n` is:
 
         .. math::
-            :numbered: False
 
             \begin{align}
             p_1 &= 0 \\