diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad81ada..cfcfc65 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,11 @@ changes, see Git history.
 Each release is tagged in Git and on the Docker repository
 [`scottlamb/moonfire-nvr`](https://hub.docker.com/r/scottlamb/moonfire-nvr).
 
+## unreleased
+
+*   fix [#182](https://github.com/scottlamb/moonfire-nvr/issues/182): error
+    on upgrade from schema 6 to schema 7 when a camera's `onvif_host` is empty.
+
 ## `v0.7.1` (2021-10-27)
 
 *   bugfix: editing a camera from `nvr config` would erroneously clear the
diff --git a/server/db/upgrade/v6_to_v7.rs b/server/db/upgrade/v6_to_v7.rs
index 9bf28ab..3e63c03 100644
--- a/server/db/upgrade/v6_to_v7.rs
+++ b/server/db/upgrade/v6_to_v7.rs
@@ -3,7 +3,7 @@
 // SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception
 
 /// Upgrades a version 6 schema to a version 7 schema.
-use failure::{format_err, Error};
+use failure::{format_err, Error, ResultExt};
 use fnv::FnvHashMap;
 use log::debug;
 use rusqlite::{named_params, params};
@@ -255,8 +255,13 @@ fn copy_cameras(tx: &rusqlite::Transaction) -> Result<(), Error> {
         let config = CameraConfig {
             description: description.take().unwrap_or_default(),
             onvif_base_url: onvif_host
+                // Older releases set the onvif host to the empty string instead
+                // of using a SQL NULL, so convert empty to None here.
+                // https://github.com/scottlamb/moonfire-nvr/issues/182
+                .filter(|h| !h.is_empty())
                 .map(|h| Url::parse(&format!("http://{}/", h)))
-                .transpose()?,
+                .transpose()
+                .with_context(|_| "bad onvif_host")?,
             username: username.take().unwrap_or_default(),
             password: password.take().unwrap_or_default(),
             ..Default::default()