diff --git a/configure.ac b/configure.ac
index 0575427..1d053f8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,6 +7,9 @@ AM_INIT_AUTOMAKE
 AC_CONFIG_SRCDIR([BioBloomMaker/BioBloomMaker.cpp])
 AC_CONFIG_HEADER([config.h])
 
+
+AC_REVISION([m4_esyscmd([./tools/configure.commit])])
+
 AC_PROG_RANLIB
 
 # Checks for programs.
diff --git a/tools/configure.commit b/tools/configure.commit
new file mode 100755
index 0000000..b6c1b98
--- /dev/null
+++ b/tools/configure.commit
@@ -0,0 +1,10 @@
+#! /bin/sh
+# Display the SHA1 of the commit in which configure.ac was last modified.
+# If it's not checked in yet, use the SHA1 of HEAD plus -dirty.
+
+if [ ! -d .git ] ; then
+  # if no .git directory, assume they're not using Git
+  printf 'no_git'
+else
+  git describe --abbrev=4 --dirty --always --tags | xargs echo -n
+fi
\ No newline at end of file