diff --git a/pandas/core/series.py b/pandas/core/series.py
index 1d6f770d92795..d1edbc5ec5e56 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -951,7 +951,10 @@ def _set_with(self, key, value):
 
             if not isinstance(key, (list, Series, np.ndarray, Series)):
                 try:
-                    key = list(key)
+                    if isinstance(key, compat.string_types):
+                        key = [key]
+                    else:
+                        key = list(key)
                 except Exception:
                     key = [key]