diff --git a/data.c b/data.c
index 582ab64..1dd2c43 100644
--- a/data.c
+++ b/data.c
@@ -73,7 +73,7 @@ int srv_open(char *basedir, int auto_upgrade)
                     ret = db_upgrade(&error);
                 else {
                     if (xs_number_get(xs_dict_get(srv_config, "layout")) < db_layout)
-                        error = xs_fmt("ERROR: db layout changed - execute 'snac upgrade' first");
+                        error = xs_fmt("ERROR: disk layout changed - execute 'snac upgrade' first");
                     else
                         ret = 1;
                 }
diff --git a/doc/snac.1 b/doc/snac.1
index 5303bc8..3e34725 100644
--- a/doc/snac.1
+++ b/doc/snac.1
@@ -145,6 +145,11 @@ Initializes the database. This is an interactive command; necessary
 information will be prompted for. The
 .Ar basedir
 directory must not exist.
+.It Cm upgrade Ar basedir
+Upgrades the database disk layout after installing a new version.
+Only necessary if
+.Nm
+complains and demands it.
 .It Cm purge Ar basedir
 Purges old data from the timeline of all users.
 .It Cm adduser Ar basedir Op uid
diff --git a/doc/snac.8 b/doc/snac.8
index a241158..82ded62 100644
--- a/doc/snac.8
+++ b/doc/snac.8
@@ -69,6 +69,15 @@ startup scripts and configuration data in the
 directory.
 For other operating systems, please read the appropriate documentation
 on how to install a daemon as a non-root service.
+.Ss Upgrading to a new version
+Sometimes, the database disk layout changes between versions. If there
+is such a change,
+.Nm
+will refuse to run and require an upgrade. Do this by running
+.Bd -literal -offset indent
+snac upgrade $HOME/snac-data
+.Ed
+.Pp
 .Ss Server Setup
 .Pp
 An http server with TLS and proxying support must already be