diff --git a/src/saveload/extended_ver_sl.cpp b/src/saveload/extended_ver_sl.cpp
index be40cad17b..bdb490917e 100644
--- a/src/saveload/extended_ver_sl.cpp
+++ b/src/saveload/extended_ver_sl.cpp
@@ -45,6 +45,7 @@ std::vector<uint32> _sl_xv_discardable_chunk_ids;           ///< list of chunks
 static const uint32 _sl_xv_slxi_chunk_version = 0;          ///< current version os SLXI chunk
 
 const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
+	{ XSLFI_ENH_VIEWPORT_PLANS,     XSCF_IGNORABLE_ALL,     1,                                    1, "enh_viewport_plans",    NULL, NULL, "PLAN,PLLN" },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, NULL, NULL, NULL, NULL },// This is the end marker
 };
 
diff --git a/src/saveload/extended_ver_sl.h b/src/saveload/extended_ver_sl.h
index 39a03478c2..befbf70724 100644
--- a/src/saveload/extended_ver_sl.h
+++ b/src/saveload/extended_ver_sl.h
@@ -21,6 +21,7 @@
  */
 enum SlXvFeatureIndex {
 	XSLFI_NULL                          = 0,      ///< Unused value, to indicate that no extended feature test is in use
+	XSLFI_ENH_VIEWPORT_PLANS,                     ///< Enhanced viewport patch: plans
 
 	XSLFI_SIZE,                                   ///< Total count of features, including null feature
 };