diff --git a/composer/schema/grid/field.py b/composer/schema/grid/field.py
index f3e2345..633e69b 100644
--- a/composer/schema/grid/field.py
+++ b/composer/schema/grid/field.py
@@ -62,9 +62,9 @@ class GridFieldInstance(ListFieldInstance):
         # TODO: marshall values!
         v = value or []
         for row in v:
-            for k, v in row.items():
-                if isinstance(v, basestring):
-                    row[k] = v.replace('\n', '\\n')
+            for k, vr in row.items():
+                if isinstance(vr, basestring):
+                    row[k] = vr.replace('\n', '\\n')
         empty = {}
         for fi in self.columnFieldInstances:
             default = fi.default