diff --git a/bin/cache/README.md b/bin/cache/README.md
index c7f88be937..ff30fed7be 100644
--- a/bin/cache/README.md
+++ b/bin/cache/README.md
@@ -1,3 +1,5 @@
 # Binary cache
 
 This directory contains a cache of binary artifacts used by the Flutter tools.
+
+Warning: Flutter tools will sometimes automatically delete files in this directory.