diff --git a/UPGRADING.md b/UPGRADING.md
index e5b6947fa2..e13a2e8ca6 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -189,6 +189,8 @@ end
 
 ### Upgrading to >= 1.3.0
 
+You will need to upgrade to this version if you depend on `rack >= 2.1.0`.
+
 #### Ruby
 
 After adding dry-types, Ruby 2.4 or newer is required.