diff --git a/CHANGES.md b/CHANGES.md
new file mode 100644
index 0000000..f315493
--- /dev/null
+++ b/CHANGES.md
@@ -0,0 +1,3 @@
+# 0.1
+
+initial release, with poll and select backends.
diff --git a/nanoev-picos.opam b/nanoev-picos.opam
index 44e1230..4edf0b5 100644
--- a/nanoev-picos.opam
+++ b/nanoev-picos.opam
@@ -1,5 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
+version: "0.1"
 synopsis: "Use nanoev from picos"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
diff --git a/nanoev-posix.opam b/nanoev-posix.opam
index b9df267..7f42615 100644
--- a/nanoev-posix.opam
+++ b/nanoev-posix.opam
@@ -1,5 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
+version: "0.1"
 synopsis: "Use mtime+iomux (posix compliant) as a backend for nanoev"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
diff --git a/nanoev.opam b/nanoev.opam
index 8268f40..6c9e1ea 100644
--- a/nanoev.opam
+++ b/nanoev.opam
@@ -1,5 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
+version: "0.1"
 synopsis: "Tiny event loop abstraction"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
diff --git a/nanoev_tiny_httpd.opam b/nanoev_tiny_httpd.opam
index 83e2b5a..a68cf32 100644
--- a/nanoev_tiny_httpd.opam
+++ b/nanoev_tiny_httpd.opam
@@ -1,5 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
+version: "0.1"
 synopsis: "Use nanoev as a basis for tiny_httpd"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]