diff --git a/rslib/src/dbcheck.rs b/rslib/src/dbcheck.rs
index b0bf876d7..be96029b0 100644
--- a/rslib/src/dbcheck.rs
+++ b/rslib/src/dbcheck.rs
@@ -5,6 +5,7 @@ use std::collections::HashSet;
 use std::sync::Arc;
 
 use anki_i18n::I18n;
+use anki_proto::notetypes::stock_notetype::OriginalStockKind;
 use itertools::Itertools;
 use tracing::debug;
 
@@ -233,7 +234,7 @@ impl Collection {
         for (ntid, group) in &nids_by_notetype.into_iter().group_by(|tup| tup.0) {
             debug!("check notetype: {}", ntid);
             let mut group = group.peekable();
-            let nt = match self.get_notetype(ntid)? {
+            let mut nt = match self.get_notetype(ntid)? {
                 None => {
                     let first_note = self.storage.get_note(group.peek().unwrap().1)?.unwrap();
                     out.notetypes_recovered += 1;
@@ -242,6 +243,8 @@ impl Collection {
                 Some(nt) => nt,
             };
 
+            self.add_missing_field_tags(Arc::make_mut(&mut nt))?;
+
             let mut genctx = None;
             for (_, nid) in group {
                 progress.increment(|p| {
@@ -427,6 +430,30 @@ impl Collection {
         }
         Ok(num_invalid_ids)
     }
+    fn add_missing_field_tags(&mut self, nt: &mut Notetype) -> Result<()> {
+        // we only try to fix I/O, as the other notetypes have been in circulation too
+        // long, and there's too much of a risk that the user has reordered the fields
+        // already. We could try to match on field name in the future though.
+        let usn = self.usn()?;
+        if let OriginalStockKind::ImageOcclusion = nt.config.original_stock_kind() {
+            let mut changed = false;
+            if nt.fields.len() >= 5 {
+                for i in 0..5 {
+                    let conf = &mut nt.fields[i].config;
+                    if !conf.prevent_deletion {
+                        changed = true;
+                        conf.prevent_deletion = true;
+                        conf.tag = Some(i as u32);
+                    }
+                }
+            }
+            if changed {
+                nt.set_modified(usn);
+                self.add_or_update_notetype_with_existing_id_inner(nt, None, usn, true)?;
+            }
+        }
+        Ok(())
+    }
 }
 
 #[cfg(test)]
diff --git a/rslib/src/notetype/stock.rs b/rslib/src/notetype/stock.rs
index 71f1308f8..c06cd8e90 100644
--- a/rslib/src/notetype/stock.rs
+++ b/rslib/src/notetype/stock.rs
@@ -2,11 +2,11 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use anki_i18n::I18n;
-use anki_proto::notetypes::ClozeField;
 use anki_proto::notetypes::notetype::config::Kind as NotetypeKind;
 use anki_proto::notetypes::stock_notetype::Kind;
 pub(crate) use anki_proto::notetypes::stock_notetype::Kind as StockKind;
 use anki_proto::notetypes::stock_notetype::OriginalStockKind;
+use anki_proto::notetypes::ClozeField;
 
 use super::NotetypeConfig;
 use crate::config::ConfigEntry;