diff --git a/README.md b/README.md
index 167a298ff..9d92ccd55 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ CotEditor is a pure document-based Cocoa application written in Swift.
 ### Development Environment
 
 - macOS 11 Big Sur
-- Xcode 12.3
+- Xcode 12.4
 - Swift 5.3
 - Sandbox enabled