diff --git a/milli/Cargo.toml b/milli/Cargo.toml
index 1295c4384..64497bc13 100644
--- a/milli/Cargo.toml
+++ b/milli/Cargo.toml
@@ -18,6 +18,7 @@ flatten-serde-json = { path = "../flatten-serde-json" }
 grenad = { version = "0.4.1", default-features = false, features = ["tempfile"] }
 geoutils = "0.4.1"
 heed = { git = "https://github.com/meilisearch/heed", tag = "v0.12.1", default-features = false, features = ["lmdb", "sync-read-txn"] }
+json-depth-checker = { path = "../json-depth-checker" }
 levenshtein_automata = { version = "0.2.1", features = ["fst_automaton"] }
 meilisearch-tokenizer = { git = "https://github.com/meilisearch/tokenizer.git", tag = "v0.2.9" }
 memmap2 = "0.5.3"
diff --git a/milli/src/update/index_documents/transform.rs b/milli/src/update/index_documents/transform.rs
index cbb6ed428..e94eb170b 100644
--- a/milli/src/update/index_documents/transform.rs
+++ b/milli/src/update/index_documents/transform.rs
@@ -286,9 +286,11 @@ impl<'a, 'i> Transform<'a, 'i> {
                     })?;
 
                 self.original_sorter.insert(&docid.to_be_bytes(), base_obkv)?;
-                let buffer = self.flatten_from_fields_ids_map(KvReader::new(&base_obkv))?;
-
-                self.flattened_sorter.insert(docid.to_be_bytes(), &buffer)?;
+                if let Some(buffer) = self.flatten_from_fields_ids_map(KvReader::new(&base_obkv))? {
+                    self.flattened_sorter.insert(docid.to_be_bytes(), &buffer)?;
+                } else {
+                    self.flattened_sorter.insert(docid.to_be_bytes(), base_obkv)?;
+                }
             } else {
                 self.new_documents_ids.insert(docid);
             }
@@ -300,8 +302,13 @@ impl<'a, 'i> Transform<'a, 'i> {
             if let Some(flatten) = flattened_document {
                 self.flattened_sorter.insert(docid.to_be_bytes(), &flatten)?;
             } else {
-                let buffer = self.flatten_from_fields_ids_map(KvReader::new(&obkv_buffer))?;
-                self.flattened_sorter.insert(docid.to_be_bytes(), &buffer)?;
+                if let Some(buffer) =
+                    self.flatten_from_fields_ids_map(KvReader::new(&obkv_buffer))?
+                {
+                    self.flattened_sorter.insert(docid.to_be_bytes(), &buffer)?;
+                } else {
+                    self.flattened_sorter.insert(docid.to_be_bytes(), obkv_buffer.clone())?;
+                }
             }
 
             progress_callback(UpdateIndexingStep::RemapDocumentAddition {
@@ -326,8 +333,15 @@ impl<'a, 'i> Transform<'a, 'i> {
     }
 
     // Flatten a document from the fields ids map contained in self and insert the new
-    // created fields.
-    fn flatten_from_fields_ids_map(&mut self, obkv: KvReader<FieldId>) -> Result<Vec<u8>> {
+    // created fields. Returns `None` if the document doesn't need to be flattened.
+    fn flatten_from_fields_ids_map(&mut self, obkv: KvReader<FieldId>) -> Result<Option<Vec<u8>>> {
+        if obkv
+            .iter()
+            .all(|(_, value)| !json_depth_checker::should_flatten_from_unchecked_slice(value))
+        {
+            return Ok(None);
+        }
+
         let mut doc = serde_json::Map::new();
 
         for (k, v) in obkv.iter() {
@@ -357,7 +371,7 @@ impl<'a, 'i> Transform<'a, 'i> {
             writer.insert(fid, &value)?;
         }
 
-        Ok(buffer)
+        Ok(Some(buffer))
     }
 
     // Flatten a document from a field mapping generated by [create_fields_mapping]