diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index eb1f455240..a6107c7374 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -84,15 +84,20 @@ Changed
   way to find out about this failure would be to inspect the ``st2rulesengine`` service logs.
   (improvement) #4231
 
+Fixed
+~~~~~
+
+* Fix an issue with ``AttributeError: module 'enum' has no attribute 'IntFlag'`` error which would
+  appear when using Python 3 for a particular pack virtual environment and running on RHEL /
+  CentOS. (bug fix) #4297
+
 Deprecated
 ~~~~~~~~~~
 
-* The CloudSlang runner is now deprecated. In StackStorm 3.1 it will be removed from the core StackStorm codebase.
-  The runner code will be moved to a separate repository, and no longer maintained by the core StackStorm team.
-  Users will still be able to install and use this runner, but it will require additional steps to install.
-
-Fixed
-~~~~~
+* The CloudSlang runner is now deprecated. In StackStorm 3.1 it will be removed from the core
+  StackStorm codebase. The runner code will be moved to a separate repository, and no longer
+  maintained by the core StackStorm team. Users will still be able to install and use this runner,
+  but it will require additional steps to install.
 
 2.8.1 - July 18, 2018
 ---------------------
diff --git a/st2common/st2common/util/sandboxing.py b/st2common/st2common/util/sandboxing.py
index 8b1f388446..eea7fc8cbe 100644
--- a/st2common/st2common/util/sandboxing.py
+++ b/st2common/st2common/util/sandboxing.py
@@ -151,14 +151,19 @@ def get_sandbox_python_path_for_python_action(pack, inherit_from_parent=True,
         uses_python3 = False
 
     if uses_python3:
-        # Add Python 3 lib/site-packages directory infront of the system site packages
-        # This is important because we want Python 3 compatible libraries to be used from
-        # the pack virtual environment and not system ones
+        # Add Python 3 lib directory (lib/python3.x) in front of the PYTHONPATH. This way we avoid
+        # issues with scripts trying to use packages / modules from Python 2.7 site-packages
+        # directory instead of the versions from Python 3 stdlib.
+        python3_lib_directory = os.path.join(pack_virtualenv_lib_path, virtualenv_directories[0])
+
+        # Add Python 3 site-packages directory (lib/python3.x/site-packages) in front of the Python
+        # 2.7 system site-packages This is important because we want Python 3 compatible libraries
+        # to be used from the pack virtual environment and not system ones.
         python3_site_packages_directory = os.path.join(pack_virtualenv_lib_path,
                                                        virtualenv_directories[0],
                                                        'site-packages')
-        sandbox_python_path = (python3_site_packages_directory + ':' + pack_actions_lib_paths +
-                               ':' + sandbox_python_path)
+        sandbox_python_path = (python3_lib_directory + ':' + python3_site_packages_directory + ':' +
+                               pack_actions_lib_paths + ':' + sandbox_python_path)
 
     return sandbox_python_path
 
diff --git a/st2common/tests/unit/test_util_sandboxing.py b/st2common/tests/unit/test_util_sandboxing.py
index 7e6bf8c42e..97477e235f 100644
--- a/st2common/tests/unit/test_util_sandboxing.py
+++ b/st2common/tests/unit/test_util_sandboxing.py
@@ -141,13 +141,16 @@ def test_get_sandbox_python_path_for_python_action_python3_used_for_venv(self,
                                                                 inherit_parent_virtualenv=False)
 
         split = python_path.strip(':').split(':')
-        self.assertEqual(len(split), 2)
+        self.assertEqual(len(split), 3)
 
-        # First entry should be python3 site-packages dir from venv
-        self.assertTrue('virtualenvs/dummy_pack/lib/python3.6/site-packages' in split[0])
+        # First entry should be lib/python3 dir from venv
+        self.assertTrue('virtualenvs/dummy_pack/lib/python3.6' in split[0])
 
-        # Second entry should be actions/lib dir from pack root directory
-        self.assertTrue('packs/dummy_pack/actions/lib/' in split[1])
+        # Second entry should be python3 site-packages dir from venv
+        self.assertTrue('virtualenvs/dummy_pack/lib/python3.6/site-packages' in split[1])
+
+        # Third entry should be actions/lib dir from pack root directory
+        self.assertTrue('packs/dummy_pack/actions/lib/' in split[2])
 
         # Inherit python path from current process
         # Mock the current process python path
@@ -156,7 +159,8 @@ def test_get_sandbox_python_path_for_python_action_python3_used_for_venv(self,
         python_path = get_sandbox_python_path_for_python_action(pack='dummy_pack',
                                                                 inherit_from_parent=True,
                                                                 inherit_parent_virtualenv=False)
-        expected = ('/tmp/virtualenvs/dummy_pack/lib/python3.6/site-packages:'
+        expected = ('/tmp/virtualenvs/dummy_pack/lib/python3.6:'
+                    '/tmp/virtualenvs/dummy_pack/lib/python3.6/site-packages:'
                     '/tmp/packs/dummy_pack/actions/lib/::/data/test1:/data/test2')
         self.assertEqual(python_path, expected)
 
@@ -174,7 +178,8 @@ def test_get_sandbox_python_path_for_python_action_python3_used_for_venv(self,
                                                                 inherit_from_parent=True,
                                                                 inherit_parent_virtualenv=True)
 
-        expected = ('/tmp/virtualenvs/dummy_pack/lib/python3.6/site-packages:'
+        expected = ('/tmp/virtualenvs/dummy_pack/lib/python3.6:'
+                    '/tmp/virtualenvs/dummy_pack/lib/python3.6/site-packages:'
                     '/tmp/packs/dummy_pack/actions/lib/::/data/test1:/data/test2:'
                     '%s/virtualenvtest' % (sys.prefix))
         self.assertEqual(python_path, expected)