diff --git a/pipenv/resolver.py b/pipenv/resolver.py
index e27e5889..446c1d8a 100644
--- a/pipenv/resolver.py
+++ b/pipenv/resolver.py
@@ -32,7 +32,7 @@ from docopt import docopt
 def cleanup_sysargv(argv):
 
     new = []
-    for arg in argv.copy():
+    for arg in argv[:]:
         if arg.startswith('-e '):
             new.append(arg)
             del argv[argv.index(arg)]