diff --git a/boa/__init__.py b/boa/__init__.py
index 3e025e68..9f595984 100644
--- a/boa/__init__.py
+++ b/boa/__init__.py
@@ -41,16 +41,16 @@ def swap_env(new_env):
         yield
 
 
-def set_env(new_env):
+def _set_env(new):
     global env
-    get_env = lambda: env  # noqa: E731
+    env = new
+    Env._singleton = new
 
-    def setter(new):
-        global env
-        env = new
-        Env._singleton = new
 
-    return Open(get_env, setter, new_env)
+def set_env(new_env):
+    global env
+    get_env = lambda: env  # noqa: E731
+    return Open(get_env, _set_env, new_env)
 
 
 def fork(