diff --git a/autonomic/system.py b/autonomic/system.py
index 82f9dd3..fa7cb10 100644
--- a/autonomic/system.py
+++ b/autonomic/system.py
@@ -21,8 +21,9 @@ def run_command(command, cwd=None, output=False, extra_env=None):
     env.update({"REMOTE_USER": username})
     env.update({"ANSIBLE_USER": username})
 
-    for key, val in extra_env.items():
-        env.update({key: val})
+    if extra_env:
+        for key, val in extra_env.items():
+            env.update({key: val})
 
     try:
         if cwd: