diff --git a/README.md b/README.md
index bd7a57fc..1120d775 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@
  - [Math](#math)   
     - [min](#min)
     - [max](#max)
+    - [sum](#sum)
     - [percentage](#percentage)
     - [ceil](#ceil)
     - [floor](#floor)