diff --git a/build.sh b/build.sh
index 45c1f45..59a4376 100755
--- a/build.sh
+++ b/build.sh
@@ -18,7 +18,7 @@ set -eu
 # moves -- and this repo's rename proved it does. The published tree is a CMake *install* tree,
 # which derives its prefix from its own location; nothing here depends on cache state.
 TOOLCHAIN_REPO="ModernMavericks/swift-toolchain"
-TOOLCHAIN_REF="6.3.3-mavericks.1"   # renovate: github-releases ModernMavericks/swift-toolchain
+TOOLCHAIN_REF="6.3.3-mavericks.4"   # renovate: github-releases ModernMavericks/swift-toolchain
 SWIFT_VERSION="6.3.3"   # renovate: swiftlang/swift
 SWIFT_SHA="064859e41d68596f486c5d724401cb370f260409"          # commit at SWIFT_TAG; Renovate moves it with SWIFT_VERSION
 # DERIVED from SWIFT_VERSION, never repeated: a Renovate bump rewrites one line, and a tag left