--- a/support/mkversion
+++ b/support/mkversion
@@ -10,6 +10,18 @@
 version="$1"
 extra="$2"
 string="INN $version"
+
+# use the date in the Debian package version, if there is one
+if [ "$extra" = "prerelease" ]; then
+  debian_version="$(dpkg-parsechangelog -SVersion)"
+  debian_version="${debian_version%~bpo[0-9]*+[0-9]*}"
+  debian_version="${debian_version%-*}"
+  debian_prerelease="${debian_version#*~}"
+  if [ "$debian_version" != "$debian_prerelease" ]; then
+    extra="$debian_prerelease $extra"
+  fi
+fi
+
 if [ x"$extra" = x"prerelease" ]; then
     date=$(date +%Y%m%d)
     # Ensure a reproducible build when the source code has not changed,
