diff --git a/jedi/api/environment.py b/jedi/api/environment.py
index 0b376067..89e47163 100644
--- a/jedi/api/environment.py
+++ b/jedi/api/environment.py
@@ -61,7 +61,7 @@ class Environment(_BaseEnvironment):
     """
     _subprocess = None
 
-    def __init__(self, executable, env_vars={}):
+    def __init__(self, executable, env_vars=None):
         self._start_executable = executable
         self._env_vars = env_vars
         # Initialize the environment
@@ -136,7 +136,7 @@ class _SameEnvironmentMixin(object):
         self._start_executable = self.executable = sys.executable
         self.path = sys.prefix
         self.version_info = _VersionInfo(*sys.version_info[:3])
-        self._env_vars = {}
+        self._env_vars = None
 
 
 class SameEnvironment(_SameEnvironmentMixin, Environment):
@@ -379,7 +379,7 @@ def create_environment(path, safe=True, **kwargs):
     return _create_environment(path, safe, **kwargs)
 
 
-def _create_environment(path, safe=True, env_vars={}):
+def _create_environment(path, safe=True, env_vars=None):
     if os.path.isfile(path):
         _assert_safe(path, safe)
         return Environment(path, env_vars=env_vars)
diff --git a/jedi/inference/compiled/subprocess/__init__.py b/jedi/inference/compiled/subprocess/__init__.py
index 56c03df9..35724a48 100644
--- a/jedi/inference/compiled/subprocess/__init__.py
+++ b/jedi/inference/compiled/subprocess/__init__.py
@@ -156,21 +156,12 @@ class CompiledSubprocess(object):
     # Start with 2, gets set after _get_info.
     _pickle_protocol = 2
 
-    def __init__(self, executable, env_vars={}):
+    def __init__(self, executable, env_vars=None):
         self._executable = executable
-        self._env_vars = dict(env_vars)
+        self._env_vars = env_vars
         self._inference_state_deletion_queue = queue.deque()
         self._cleanup_callable = lambda: None
 
-        # Use explicit envionment to ensure reliable results (#1540)
-        if os.name == 'nt':
-            # if SYSTEMROOT (or case variant) exists in environment,
-            # ensure it goes to subprocess
-            for k, v in os.environ.items():
-                if 'SYSTEMROOT' == k.upper():
-                    self._env_vars.update({k: os.environ[k]})
-                    break  # don't risk multiple entries
-
     def __repr__(self):
         pid = os.getpid()
         return '<%s _executable=%r, _pickle_protocol=%r, is_crashed=%r, pid=%r>' % (