diff --git a/README.md b/README.md
index 1aeccc8..fcbe995 100644
--- a/README.md
+++ b/README.md
@@ -67,6 +67,13 @@ That's all you need to do - after git-crypt is set up (either with
 `git-crypt init` or `git-crypt unlock`), you can use git normally -
 encryption and decryption happen transparently.
 
+To check if a file will be encrypted before committing it:
+
+    git add path/new/file
+    git diff --cached
+    
+The diff output will show `Binary files ... ... differ` instead of the contents of the file.
+
 Current Status
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