diff --git a/milli/src/update/snapshots/word_prefix_pair_proximity_docids.rs/test_update/update/word_prefix_pair_proximity_docids.hash.snap b/milli/src/update/snapshots/word_prefix_pair_proximity_docids.rs/test_update/update/word_prefix_pair_proximity_docids.hash.snap
index 574cfa72f..a39ee07b5 100644
--- a/milli/src/update/snapshots/word_prefix_pair_proximity_docids.rs/test_update/update/word_prefix_pair_proximity_docids.hash.snap
+++ b/milli/src/update/snapshots/word_prefix_pair_proximity_docids.rs/test_update/update/word_prefix_pair_proximity_docids.hash.snap
@@ -1,4 +1,4 @@
 ---
 source: milli/src/update/word_prefix_pair_proximity_docids.rs
 ---
-53e42e513b83885139e4f6d817888561
+5ed4bf83317b10962a55ade353427bdd
diff --git a/milli/src/update/word_prefix_pair_proximity_docids.rs b/milli/src/update/word_prefix_pair_proximity_docids.rs
index 90430c0dd..bcd940410 100644
--- a/milli/src/update/word_prefix_pair_proximity_docids.rs
+++ b/milli/src/update/word_prefix_pair_proximity_docids.rs
@@ -554,8 +554,8 @@ fn insert_into_database(
                             process: "get-put-merge",
                         }
                     })?;
-            // safety: we don't keep references from inside the LMDB database.
-            unsafe { iter.put_current(key, &val)? };
+            // safety: we use the new_key, not the one from the database iterator, to avoid undefined behaviour
+            unsafe { iter.put_current(new_key, &val)? };
         }
         _ => {
             drop(iter);
@@ -579,7 +579,7 @@ pub fn write_into_lmdb_database_without_merging(
         let mut out_iter = database.iter_mut::<_, ByteSlice, ByteSlice>(wtxn)?;
         let mut cursor = reader.into_cursor()?;
         while let Some((k, v)) = cursor.move_on_next()? {
-            // safety: we don't keep references from inside the LMDB database.
+            // safety: the key comes from the grenad reader, not the database
             unsafe { out_iter.append(k, v)? };
         }
     } else {