diff --git a/fwdpy11/_tables_to_tskit.py b/fwdpy11/_tables_to_tskit.py
index <HASH>..<HASH> 100644
--- a/fwdpy11/_tables_to_tskit.py
+++ b/fwdpy11/_tables_to_tskit.py
@@ -32,7 +32,8 @@ def _generate_mutation_metadata(pop):
              'label': m.label,
              'esizes': list(m.esizes),
              'heffects': list(m.heffects),
-             'neutral': m.neutral}
+             'neutral': m.neutral,
+             'key': mr.key}
         muts.append(str(d).encode('utf-8'))
     return tskit.pack_bytes(muts)
Add mutation key to mutation metadata when dumping tables to tskit.