diff --git a/crates/storage/libmdbx-rs/src/transaction.rs b/crates/storage/libmdbx-rs/src/transaction.rs
index 67f28ae9e3..20e315bb38 100644
--- a/crates/storage/libmdbx-rs/src/transaction.rs
+++ b/crates/storage/libmdbx-rs/src/transaction.rs
@@ -412,8 +412,16 @@ impl Transaction<RW> {
     /// Returns a buffer which can be used to write a value into the item at the
     /// given key and with the given length. The buffer must be completely
     /// filled by the caller.
+    ///
+    /// This should not be used on dupsort tables.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the returned buffer is not used after the transaction is
+    /// committed or aborted, or if another value is inserted. To be clear: the second call to
+    /// this function is not permitted while the returned slice is reachable.
     #[allow(clippy::mut_from_ref)]
-    pub fn reserve(
+    pub unsafe fn reserve(
         &self,
         dbi: ffi::MDBX_dbi,
         key: impl AsRef<[u8]>,
diff --git a/crates/storage/libmdbx-rs/tests/transaction.rs b/crates/storage/libmdbx-rs/tests/transaction.rs
index 81da1beada..f289b30920 100644
--- a/crates/storage/libmdbx-rs/tests/transaction.rs
+++ b/crates/storage/libmdbx-rs/tests/transaction.rs
@@ -105,8 +105,11 @@ fn test_reserve() {
     let txn = env.begin_rw_txn().unwrap();
     let dbi = txn.open_db(None).unwrap().dbi();
     {
-        let mut writer = txn.reserve(dbi, b"key1", 4, WriteFlags::empty()).unwrap();
-        writer.write_all(b"val1").unwrap();
+        unsafe {
+            // SAFETY: the returned slice is used before the transaction is committed or aborted.
+            let mut writer = txn.reserve(dbi, b"key1", 4, WriteFlags::empty()).unwrap();
+            writer.write_all(b"val1").unwrap();
+        }
     }
     txn.commit().unwrap();