diff --git a/src/index.md b/src/index.md
index f8e67c6..995098b 100644
--- a/src/index.md
+++ b/src/index.md
@@ -13,6 +13,6 @@ Computer Science & Math Student at ENS Ulm
 
 Current topics of interest:
 
- - formal verification with [lean](leanprover.github.io)
+ - formal verification with [lean](https://leanprover.github.io)
  - [Geometry of Interaction](https://ncatlab.org/nlab/show/Geometry+of+Interaction)