diff --git a/milli/src/update/index_documents/enrich.rs b/milli/src/update/index_documents/enrich.rs
index 0298f0532..d7ab89faa 100644
--- a/milli/src/update/index_documents/enrich.rs
+++ b/milli/src/update/index_documents/enrich.rs
@@ -257,12 +257,9 @@ impl fmt::Debug for DocumentId {
 }
 
 fn contained_in(selector: &str, key: &str) -> bool {
-    selector.starts_with(key)
-        && selector[key.len()..]
-            .chars()
-            .next()
-            .map(|c| c == PRIMARY_KEY_SPLIT_SYMBOL)
-            .unwrap_or(true)
+    selector.strip_prefix(key).map_or(false, |tail| {
+        tail.chars().next().map(|c| c == PRIMARY_KEY_SPLIT_SYMBOL).unwrap_or(true)
+    })
 }
 
 pub fn fetch_matching_values(value: Value, selector: &str, output: &mut Vec<Value>) {
diff --git a/milli/src/update/index_documents/mod.rs b/milli/src/update/index_documents/mod.rs
index 54599acce..c9890f93f 100644
--- a/milli/src/update/index_documents/mod.rs
+++ b/milli/src/update/index_documents/mod.rs
@@ -1627,6 +1627,58 @@ mod tests {
         assert_eq!(documents_ids, vec![3]);
     }
 
+    #[test]
+    fn retrieve_a_b_nested_document_id() {
+        let path = tempfile::tempdir().unwrap();
+        let mut options = EnvOpenOptions::new();
+        options.map_size(10 * 1024 * 1024); // 10 MB
+        let index = Index::new(options, &path).unwrap();
+        let config = IndexerConfig::default();
+
+        let mut wtxn = index.write_txn().unwrap();
+        let mut builder = update::Settings::new(&mut wtxn, &index, &config);
+        builder.set_primary_key("a.b".to_owned());
+        builder.execute(|_| ()).unwrap();
+
+        let content = documents!({ "a" : { "b" : { "c" :  1 }}});
+        let indexing_config = IndexDocumentsConfig::default();
+        let builder =
+            IndexDocuments::new(&mut wtxn, &index, &config, indexing_config.clone(), |_| ())
+                .unwrap();
+        let (_builder, user_error) = builder.add_documents(content).unwrap();
+
+        // There must be an issue with the primary key no present in the given document
+        user_error.unwrap_err();
+    }
+
+    #[test]
+    fn retrieve_a_b_c_nested_document_id() {
+        let path = tempfile::tempdir().unwrap();
+        let mut options = EnvOpenOptions::new();
+        options.map_size(10 * 1024 * 1024); // 10 MB
+        let index = Index::new(options, &path).unwrap();
+        let config = IndexerConfig::default();
+
+        let mut wtxn = index.write_txn().unwrap();
+        let mut builder = update::Settings::new(&mut wtxn, &index, &config);
+        builder.set_primary_key("a.b.c".to_owned());
+        builder.execute(|_| ()).unwrap();
+
+        let content = documents!({ "a" : { "b" : { "c" :  1 }}});
+        let indexing_config = IndexDocumentsConfig::default();
+        let builder =
+            IndexDocuments::new(&mut wtxn, &index, &config, indexing_config.clone(), |_| ())
+                .unwrap();
+        let (builder, user_error) = builder.add_documents(content).unwrap();
+        user_error.unwrap();
+        builder.execute().unwrap();
+        wtxn.commit().unwrap();
+
+        let rtxn = index.read_txn().unwrap();
+        let external_documents_ids = index.external_documents_ids(&rtxn).unwrap();
+        assert!(external_documents_ids.get("1").is_some());
+    }
+
     #[test]
     fn test_facets_generation() {
         let path = tempfile::tempdir().unwrap();