diff --git a/configure.hs b/configure.hs
index 8d1c117a71..1451d7eaa3 100644
--- a/configure.hs
+++ b/configure.hs
@@ -10,6 +10,7 @@ tests = [
 	, testCp "cp_p" "-p"
 	, testCp "cp_reflink_auto" "--reflink=auto"
 	, TestCase "uuid generator" $ selectCmd "uuid" ["uuid", "uuidgen"]
+	, TestCase "sha1sum" $ requireCmd "sha1sum" "sha1sum </dev/null"
 	, TestCase "xargs -0" $ requireCmd "xargs_0" "xargs -0 </dev/null"
 	, TestCase "rsync" $ requireCmd "rsync" "rsync --version >/dev/null"
 	]
diff --git a/debian/changelog b/debian/changelog
index 3a5f60fefe..b8d27f77e4 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,4 +1,4 @@
-git-annex (0.20) UNRELEASED; urgency=low
+git-annex (0.20) unstable; urgency=low
 
   * Preserve specified file ordering when instructed to act on multiple
     files or directories. For example, "git annex get a b" will now always
@@ -9,8 +9,9 @@ git-annex (0.20) UNRELEASED; urgency=low
   * map: New subcommand that uses graphviz to display a nice map of
     the git repository network.
   * Deal with the mtl/monads-fd conflict.
+  * configure: Check for sha1sum.
 
- -- Joey Hess <joeyh@debian.org>  Mon, 31 Jan 2011 20:06:02 -0400
+ -- Joey Hess <joeyh@debian.org>  Tue, 08 Feb 2011 18:57:24 -0400
 
 git-annex (0.19) unstable; urgency=low
 
diff --git a/doc/install.mdwn b/doc/install.mdwn
index 3c7025fa60..fc9f28ae7b 100644
--- a/doc/install.mdwn
+++ b/doc/install.mdwn
@@ -8,6 +8,7 @@ To build and use git-annex, you will need:
   (or uuidgen from util-linux)
 * `xargs`: <http://savannah.gnu.org/projects/findutils/>
 * `rsync`: <http://rsync.samba.org/>
+* `sha1sum`: <ftp://ftp.gnu.org/gnu/coreutils/>
 * Then just [[download]] git-annex and run: `make; make install`
 
 ([Ikiwiki](http://ikiwiki.info) is needed to build the documentation,