DELETE_FAST should issue an exception when the local variable is undefined.
diff --git a/Python/ceval.c b/Python/ceval.c
index 0527537..7c358db 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1337,6 +1337,13 @@
 			continue;
 
 		case DELETE_FAST:
+			x = GETLOCAL(oparg);
+			if (x == NULL) {
+				PyErr_SetObject(PyExc_NameError,
+					   PyTuple_GetItem(co->co_varnames,
+							oparg));
+				break;
+			}
 			SETLOCAL(oparg, NULL);
 			continue;