diff --git a/.gitignore b/.gitignore
index 982ee3ca..1f05dc75 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ DerivedData/
 
 # Other things to ignore:
 /node_modules
+/.swiftformat-cache
diff --git a/script/format/check b/script/format/check
index bcdfb4e1..8e4dee25 100755
--- a/script/format/check
+++ b/script/format/check
@@ -2,5 +2,7 @@
 
 set -e
 
-swift package plugin --allow-writing-to-package-directory swiftformat --lint
+# Without specifying --cache we get a warning of "Failed to write cache file at /Users/lawrence/Library/Caches/com.charcoaldesign.swiftformat/swiftformat.cache."; presumably this is to do with sandboxing restrictions imposed on Swift package scripts.
+swift package plugin --allow-writing-to-package-directory swiftformat --cache .swiftformat-cache --lint
+
 npm run format:check
diff --git a/script/format/fix b/script/format/fix
index a54cb1b5..d0a3f06f 100755
--- a/script/format/fix
+++ b/script/format/fix
@@ -2,5 +2,7 @@
 
 set -e
 
-swift package plugin --allow-writing-to-package-directory swiftformat
+# (See the `check` script for why we specify --cache. The repetition is because, according to https://github.com/nicklockwood/SwiftFormat/issues/1651#issuecomment-2009943414, you can’t use a .swiftformat file to specify the --cache option.)
+swift package plugin --allow-writing-to-package-directory swiftformat --cache .swiftformat-cache
+
 npm run format:fix