diff --git a/src/hb-open-type-private.hh b/src/hb-open-type-private.hh
index fcdee025f..c4446ce08 100644
--- a/src/hb-open-type-private.hh
+++ b/src/hb-open-type-private.hh
@@ -985,6 +985,10 @@ struct GenericSortedArrayOf : GenericArrayOf<LenType, Type>
 template <typename Type>
 struct SortedArrayOf : GenericSortedArrayOf<USHORT, Type> {};
 
+/* A sorted array with a ULONG number of elements. */
+template <typename Type>
+struct LongSortedArrayOf : GenericSortedArrayOf<ULONG, Type> {};
+
 
 } /* namespace OT */
 
diff --git a/src/hb-ot-cmap-table.hh b/src/hb-ot-cmap-table.hh
index 65434c406..b7c89ce9a 100644
--- a/src/hb-ot-cmap-table.hh
+++ b/src/hb-ot-cmap-table.hh
@@ -264,7 +264,7 @@ struct CmapSubtableLongSegmented
   USHORT	reserved;	/* Reserved; set to 0. */
   ULONG		length;		/* Byte length of this subtable. */
   ULONG		language;	/* Ignore. */
-  LongArrayOf<CmapSubtableLongGroup>
+  LongSortedArrayOf<CmapSubtableLongGroup>
 		groups;		/* Groupings. */
   public:
   DEFINE_SIZE_ARRAY (16, groups);