diff --git a/README.md b/README.md
index 0b5bbc7..2eb9189 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,14 @@
 pristine-zip
 ============
 
 Like pristine-tar, but of ZIP files: regenerate a pristine upstream zipball
 using only a small binary delta file and a revision control checkout of the
 upstream branch.
 
+# Development status
+
+Currently one works for InfoZIP and 7zip.
+
+pristine-zip is currently of proof-of-concept quality. It was only tested on
+a few ZIP files; and provides no stability guarantee if the deltas are not
+read with the same pristine-zip/InfoZIP/7zip versions as they were written.