diff --git a/st2actions/st2actions/config.py b/st2actions/st2actions/config.py
index 3ed43c3c6e..7a98134278 100644
--- a/st2actions/st2actions/config.py
+++ b/st2actions/st2actions/config.py
@@ -28,10 +28,13 @@
 
 
 def parse_args(args=None):
+    # Override oslo_config's 'OS_' env var prefix with 'ST2_'.
+    CONF._env_driver = common_config.St2EnvironmentConfigurationSource()
     CONF(
         args=args,
         version=VERSION_STRING,
         default_config_files=[DEFAULT_CONFIG_FILE_PATH],
+        use_env=True,  # Make our env var support explicit (default is True)
     )
 
 
diff --git a/st2reactor/st2reactor/cmd/trigger_re_fire.py b/st2reactor/st2reactor/cmd/trigger_re_fire.py
index 8282a5decf..acee891da6 100644
--- a/st2reactor/st2reactor/cmd/trigger_re_fire.py
+++ b/st2reactor/st2reactor/cmd/trigger_re_fire.py
@@ -48,6 +48,8 @@ def _parse_config():
     CONF.register_cli_opts(cli_opts)
     st2cfg.register_opts(ignore_errors=False)
 
+    # Override oslo_config's 'OS_' env var prefix with 'ST2_'.
+    CONF._env_driver = st2cfg.St2EnvironmentConfigurationSource()
     CONF(args=sys.argv[1:])