diff --git a/plume-models/src/users.rs b/plume-models/src/users.rs
index d6c31f65..a8243d16 100644
--- a/plume-models/src/users.rs
+++ b/plume-models/src/users.rs
@@ -54,6 +54,7 @@ pub enum Role {
 }
 
 #[derive(Queryable, Identifiable, Clone, Debug, AsChangeset)]
+#[changeset_options(treat_none_as_null = "true")]
 pub struct User {
     pub id: i32,
     pub username: String,
diff --git a/src/routes/user.rs b/src/routes/user.rs
index 2cc48302..2a952d1d 100644
--- a/src/routes/user.rs
+++ b/src/routes/user.rs
@@ -399,7 +399,10 @@ pub fn update(
         )
         .0,
     );
-    user.preferred_theme = form.theme.clone();
+    user.preferred_theme = form
+        .theme
+        .clone()
+        .and_then(|t| if &t == "" { None } else { Some(t) });
     user.hide_custom_css = form.hide_custom_css;
     let _: User = user.save_changes(&*conn).map_err(Error::from)?;