diff --git a/contents/winrm_session.py b/contents/winrm_session.py
index 0ea4402..1fa187f 100644
--- a/contents/winrm_session.py
+++ b/contents/winrm_session.py
@@ -29,7 +29,7 @@
 PY3 = sys.version_info[0] == 3
 PY34 = sys.version_info[0:2] >= (3, 4)
 RD = "RD_"
-RD_COMMAND = "RD_EXEC_COMMAND"
+INVALID_CHAR = "%"
 
 if PY3:
     string_types = str,
@@ -55,7 +55,7 @@ def run_cmd(self, command, args=(), out_stream=None, err_stream=None):
 
     envs = {}
     for a in os.environ:
-        if a.startswith(RD) and a != RD_COMMAND:
+        if a.startswith(RD) and INVALID_CHAR not in os.environ[a]:
            envs.update({a:os.getenv(a)})
 
     # TODO optimize perf. Do not call open/close shell every time