diff --git a/python/hal9/iobind.py b/python/hal9/iobind.py
index 9e8b6b87..32ebb8ea 100644
--- a/python/hal9/iobind.py
+++ b/python/hal9/iobind.py
@@ -85,7 +85,7 @@ def save(name, contents = None, hidden = False, files = None):
     if isinstance(contents, str):
       file_path.write_text(contents)
     else:
-      if extension == "json":
+      if extension == "pkl":
         with open(file_path, 'wb') as file:
           pickle.dump(contents, file)
       else:
diff --git a/python/pyproject.toml b/python/pyproject.toml
index 56003c53..fc99c3cb 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "hal9"
-version = "2.5.7"
+version = "2.5.8"
 description = ""
 authors = ["Javier Luraschi <javier@hal9.ai>"]
 readme = "README.md"