diff --git a/src/OT/Layout/GSUB/AlternateSet.hh b/src/OT/Layout/GSUB/AlternateSet.hh
index 9904cbcc1..a5dcb6535 100644
--- a/src/OT/Layout/GSUB/AlternateSet.hh
+++ b/src/OT/Layout/GSUB/AlternateSet.hh
@@ -7,10 +7,11 @@ namespace OT {
 namespace Layout {
 namespace GSUB_impl {
 
+template <typename Types>
 struct AlternateSet
 {
   protected:
-  Array16Of<HBGlyphID16>
+  Array16Of<typename Types::HBGlyphID>
                 alternates;             /* Array of alternate GlyphIDs--in
                                          * arbitrary order */
   public:
diff --git a/src/OT/Layout/GSUB/AlternateSubst.hh b/src/OT/Layout/GSUB/AlternateSubst.hh
index c87e1412f..2ff50d1ff 100644
--- a/src/OT/Layout/GSUB/AlternateSubst.hh
+++ b/src/OT/Layout/GSUB/AlternateSubst.hh
@@ -12,8 +12,8 @@ struct AlternateSubst
 {
   protected:
   union {
-  HBUINT16              format;         /* Format identifier */
-  AlternateSubstFormat1 format1;
+  HBUINT16				format;         /* Format identifier */
+  AlternateSubstFormat1_2<SmallTypes>	format1;
   } u;
   public:
 
diff --git a/src/OT/Layout/GSUB/AlternateSubstFormat1.hh b/src/OT/Layout/GSUB/AlternateSubstFormat1.hh
index 125d8f927..c1747a2c5 100644
--- a/src/OT/Layout/GSUB/AlternateSubstFormat1.hh
+++ b/src/OT/Layout/GSUB/AlternateSubstFormat1.hh
@@ -8,18 +8,19 @@ namespace OT {
 namespace Layout {
 namespace GSUB_impl {
 
-struct AlternateSubstFormat1
+template <typename Types>
+struct AlternateSubstFormat1_2
 {
   protected:
   HBUINT16      format;                 /* Format identifier--format = 1 */
-  Offset16To<Coverage>
+  typename Types::template OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of Substitution table */
-  Array16OfOffset16To<AlternateSet>
+  Array16Of<typename Types::template OffsetTo<AlternateSet<Types>>>
                 alternateSet;           /* Array of AlternateSet tables
                                          * ordered by Coverage Index */
   public:
-  DEFINE_SIZE_ARRAY (6, alternateSet);
+  DEFINE_SIZE_ARRAY (2 + 2 * Types::size, alternateSet);
 
   bool sanitize (hb_sanitize_context_t *c) const
   {
@@ -39,7 +40,7 @@ struct AlternateSubstFormat1
     | hb_filter (c->parent_active_glyphs (), hb_first)
     | hb_map (hb_second)
     | hb_map (hb_add (this))
-    | hb_apply ([c] (const AlternateSet &_) { _.closure (c); })
+    | hb_apply ([c] (const AlternateSet<Types> &_) { _.closure (c); })
     ;
 
   }
@@ -52,7 +53,7 @@ struct AlternateSubstFormat1
     + hb_zip (this+coverage, alternateSet)
     | hb_map (hb_second)
     | hb_map (hb_add (this))
-    | hb_apply ([c] (const AlternateSet &_) { _.collect_glyphs (c); })
+    | hb_apply ([c] (const AlternateSet<Types> &_) { _.collect_glyphs (c); })
     ;
   }