diff --git a/include/__config b/include/__config
index 1fe96d0..7f6fbf0 100644
--- a/include/__config
+++ b/include/__config
@@ -34,7 +34,11 @@
 #endif
 
 #if defined(_LIBCPP_ABI_UNSTABLE) || _LIBCPP_ABI_VERSION >= 2
+// Change short string represention so that string data starts at offset 0,
+// improving its alignment in some cases.
 #define _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
+// Fix deque iterator type in order to support incomplete types.
+#define _LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
 #endif
 
 #define _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_X##_LIBCPP_Y