diff --git a/Performance.md b/Performance.md
index 32304df..d759218 100644
--- a/Performance.md
+++ b/Performance.md
@@ -149,7 +149,7 @@ This involved:
 
 For a very big project, this might happen over and over and over again per a module.
 
-</summary>
+</details>
 
 ## Preferring Base Types Over Unions