Don't mutate var
@@ -453,7 +453,7 @@ class BaseEnvironment:
kwargs['bin_path'] = env_path
if 'environment' in kwargs:
raise BuildEnvironmentError('environment can\'t be passed in via commands.')
- kwargs['environment'] = self.environment
+ kwargs['environment'] = self.environment.copy()
# ``build_env`` is passed as ``kwargs`` when it's called from a
# ``*BuildEnvironment``
