diff --git a/environment.yml b/environment.yml
index 5f7135e1..135a4e09 100644
--- a/environment.yml
+++ b/environment.yml
@@ -41,6 +41,7 @@ dependencies:
     - torchvision==0.16.1
     - transformers==4.43.4
     - yapf==0.40.2
+    - six==1.17.0
 
 variables:
   KMP_DUPLICATE_LIB_OK: "TRUE"
diff --git a/examples/generation/docking_generation/GCPN/gym-molecule/gym_molecule/envs/sascorer.py b/examples/generation/docking_generation/GCPN/gym-molecule/gym_molecule/envs/sascorer.py
index 492f2ff3..28f6a581 100644
--- a/examples/generation/docking_generation/GCPN/gym-molecule/gym_molecule/envs/sascorer.py
+++ b/examples/generation/docking_generation/GCPN/gym-molecule/gym_molecule/envs/sascorer.py
@@ -19,8 +19,8 @@
 
 from rdkit import Chem
 from rdkit.Chem import rdMolDescriptors
-from rdkit.six.moves import cPickle
-from rdkit.six import iteritems
+from six.moves import cPickle
+from six import iteritems
 
 import math
 from collections import defaultdict
diff --git a/examples/generation/docking_generation/MARS/estimator/scorer/sa_scorer.py b/examples/generation/docking_generation/MARS/estimator/scorer/sa_scorer.py
index 0e293064..7e5f4586 100644
--- a/examples/generation/docking_generation/MARS/estimator/scorer/sa_scorer.py
+++ b/examples/generation/docking_generation/MARS/estimator/scorer/sa_scorer.py
@@ -24,7 +24,7 @@
 
 from rdkit import Chem
 from rdkit.Chem import rdMolDescriptors
-from rdkit.six import iteritems
+from six import iteritems
 
 _fscores = None
 
diff --git a/requirements.txt b/requirements.txt
index b0001814..8b139d24 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,3 +17,4 @@ gget>=0.28.4,<1.0.0
 pydantic>=2.6.3,<3.0.0
 rdkit>=2023.9.5,<2024.3.1
 tiledbsoma>=1.7.2,<2.0.0
+six==1.17.0
diff --git a/tdc/chem_utils/oracle/oracle.py b/tdc/chem_utils/oracle/oracle.py
index faa6d705..6341a16b 100644
--- a/tdc/chem_utils/oracle/oracle.py
+++ b/tdc/chem_utils/oracle/oracle.py
@@ -21,7 +21,7 @@
 
     rdBase.DisableLog("rdApp.error")
     from rdkit.Chem import rdMolDescriptors
-    from rdkit.six import iteritems
+    from six import iteritems
 except:
     raise ImportError(
         "Please install rdkit by 'conda install -c conda-forge rdkit'! ")