1 files changed, 1 insertions, 1 deletions
diff --git a/setuptools/sandbox.py b/setuptools/sandbox.py
index 090cb34c..a5a01a46 100755
--- a/setuptools/sandbox.py
+++ b/setuptools/sandbox.py
@@ -85,7 +85,7 @@ def run_setup(setup_script, args):
             # exclude any encodings modules. See #285
             and not mod_name.startswith('encodings.')
         ]
-        map(sys.modules.__delitem__, del_modules)
+        list(map(sys.modules.__delitem__, del_modules))
         os.chdir(old_dir)
         sys.path[:] = save_path
         sys.argv[:] = save_argv