diff --git a/dvc/repo/experiments/serialize.py b/dvc/repo/experiments/serialize.py
index 886f5a77b..6f3cb854a 100644
--- a/dvc/repo/experiments/serialize.py
+++ b/dvc/repo/experiments/serialize.py
@@ -60,6 +60,7 @@ class SerializableExp:
         # supported in dataclasses.asdict() on all python releases
         # see https://bugs.python.org/issue35540
         params = dict(_gather_params(repo, deps=param_deps, onerror=onerror))
+        params = {k: dict(v) for k, v in params.items()}
         metrics = dict(
             _gather_metrics(
                 repo,