diff --git a/crates/milli/src/update/new/extract/vectors/mod.rs b/crates/milli/src/update/new/extract/vectors/mod.rs
index 47bd622ae..43647e786 100644
--- a/crates/milli/src/update/new/extract/vectors/mod.rs
+++ b/crates/milli/src/update/new/extract/vectors/mod.rs
@@ -111,6 +111,8 @@ impl<'extractor> Extractor<'extractor> for EmbeddingExtractor<'_, '_> {
                         let prompt = chunks.prompt();
 
                         let old_vectors = old_vectors.vectors_for_key(embedder_name)?.unwrap();
+
+                        // case where we have a `_vectors` field in the updated document
                         if let Some(new_vectors) = new_vectors.as_ref().and_then(|new_vectors| {
                             new_vectors.vectors_for_key(embedder_name).transpose()
                         }) {
@@ -130,18 +132,9 @@ impl<'extractor> Extractor<'extractor> for EmbeddingExtractor<'_, '_> {
                                             error: error.to_string(),
                                         })?,
                                 )?;
+                            // regenerate if the new `_vectors` fields is set to.
                             } else if new_vectors.regenerate {
                                 let new_rendered = prompt.render_document(
-                                    update.external_document_id(),
-                                    update.current(
-                                        &context.rtxn,
-                                        context.index,
-                                        context.db_fields_ids_map,
-                                    )?,
-                                    context.new_fields_ids_map,
-                                    &context.doc_alloc,
-                                )?;
-                                let old_rendered = prompt.render_document(
                                     update.external_document_id(),
                                     update.merged(
                                         &context.rtxn,
@@ -151,7 +144,31 @@ impl<'extractor> Extractor<'extractor> for EmbeddingExtractor<'_, '_> {
                                     context.new_fields_ids_map,
                                     &context.doc_alloc,
                                 )?;
-                                if new_rendered != old_rendered {
+                                let must_regenerate = if !old_vectors.regenerate {
+                                    // we just enabled `regenerate`
+                                    true
+                                } else {
+                                    let old_rendered = prompt.render_document(
+                                        update.external_document_id(),
+                                        update.current(
+                                            &context.rtxn,
+                                            context.index,
+                                            context.db_fields_ids_map,
+                                        )?,
+                                        context.new_fields_ids_map,
+                                        &context.doc_alloc,
+                                    );
+
+                                    if let Ok(old_rendered) = old_rendered {
+                                        // must regenerate if the rendered changed
+                                        new_rendered != old_rendered
+                                    } else {
+                                        // cannot check previous rendered, better regenerate
+                                        true
+                                    }
+                                };
+
+                                if must_regenerate {
                                     chunks.set_autogenerated(
                                         update.docid(),
                                         update.external_document_id(),
@@ -160,17 +177,8 @@ impl<'extractor> Extractor<'extractor> for EmbeddingExtractor<'_, '_> {
                                     )?;
                                 }
                             }
+                        // no `_vectors` field, so only regenerate if the document is already set to in the DB.
                         } else if old_vectors.regenerate {
-                            let old_rendered = prompt.render_document(
-                                update.external_document_id(),
-                                update.current(
-                                    &context.rtxn,
-                                    context.index,
-                                    context.db_fields_ids_map,
-                                )?,
-                                context.new_fields_ids_map,
-                                &context.doc_alloc,
-                            )?;
                             let new_rendered = prompt.render_document(
                                 update.external_document_id(),
                                 update.merged(
@@ -181,7 +189,28 @@ impl<'extractor> Extractor<'extractor> for EmbeddingExtractor<'_, '_> {
                                 context.new_fields_ids_map,
                                 &context.doc_alloc,
                             )?;
-                            if new_rendered != old_rendered {
+
+                            let must_regenerate = {
+                                let old_rendered = prompt.render_document(
+                                    update.external_document_id(),
+                                    update.current(
+                                        &context.rtxn,
+                                        context.index,
+                                        context.db_fields_ids_map,
+                                    )?,
+                                    context.new_fields_ids_map,
+                                    &context.doc_alloc,
+                                );
+                                if let Ok(old_rendered) = old_rendered {
+                                    // regenerate if the rendered version changed
+                                    new_rendered != old_rendered
+                                } else {
+                                    // if we cannot render the previous version of the documents, let's regenerate
+                                    true
+                                }
+                            };
+
+                            if must_regenerate {
                                 chunks.set_autogenerated(
                                     update.docid(),
                                     update.external_document_id(),