diff --git a/miplearn/features.py b/miplearn/features.py
index d07c4e6..1665d9b 100644
--- a/miplearn/features.py
+++ b/miplearn/features.py
@@ -243,7 +243,7 @@ class FeaturesExtractor:
                 )
                 cf = instance.get_constraint_features(cname)
                 if isinstance(cf, np.ndarray):
-                    cf = tuple(cf.tolist())
+                    cf = cf.tolist()
                 assert isinstance(cf, list), (
                     f"Constraint features must be a list. "
                     f"Found {type(cf).__name__} instead for cname={cname}."
diff --git a/setup.py b/setup.py
index e2ba662..dae8a38 100644
--- a/setup.py
+++ b/setup.py
@@ -9,7 +9,7 @@ with open("README.md", "r") as fh:
 
 setup(
     name="miplearn",
-    version="0.2.0.dev7",
+    version="0.2.0.dev8",
     author="Alinson S. Xavier",
     author_email="axavier@anl.gov",
     description="Extensible framework for Learning-Enhanced Mixed-Integer Optimization",