diff --git a/src/OT/Layout/GPOS/PairPos.hh b/src/OT/Layout/GPOS/PairPos.hh
index 8479178d3..7bf79e98b 100644
--- a/src/OT/Layout/GPOS/PairPos.hh
+++ b/src/OT/Layout/GPOS/PairPos.hh
@@ -12,9 +12,12 @@ struct PairPos
 {
   protected:
   union {
-  HBUINT16              format;         /* Format identifier */
-  PairPosFormat1        format1;
-  PairPosFormat2        format2;
+  HBUINT16			format;         /* Format identifier */
+  PairPosFormat1		format1;
+  PairPosFormat2_4<SmallTypes>	format2;
+#ifndef HB_NO_BORING_EXPANSION
+  PairPosFormat2_4<MediumTypes>	format4;
+#endif
   } u;
 
   public:
@@ -26,6 +29,9 @@ struct PairPos
     switch (u.format) {
     case 1: return_trace (c->dispatch (u.format1, std::forward<Ts> (ds)...));
     case 2: return_trace (c->dispatch (u.format2, std::forward<Ts> (ds)...));
+#ifndef HB_NO_BORING_EXPANSION
+    case 4: return_trace (c->dispatch (u.format2, std::forward<Ts> (ds)...));
+#endif
     default:return_trace (c->default_return_value ());
     }
   }
diff --git a/src/OT/Layout/GPOS/PairPosFormat2.hh b/src/OT/Layout/GPOS/PairPosFormat2.hh
index 3f5f9959c..f58bcb1b3 100644
--- a/src/OT/Layout/GPOS/PairPosFormat2.hh
+++ b/src/OT/Layout/GPOS/PairPosFormat2.hh
@@ -7,11 +7,12 @@ namespace OT {
 namespace Layout {
 namespace GPOS_impl {
 
-struct PairPosFormat2
+template <typename Types>
+struct PairPosFormat2_4
 {
   protected:
   HBUINT16      format;                 /* Format identifier--format = 2 */
-  Offset16To<Coverage>
+  typename Types::template OffsetTo<Coverage>
                 coverage;               /* Offset to Coverage table--from
                                          * beginning of subtable */
   ValueFormat   valueFormat1;           /* ValueRecord definition--for the
@@ -20,11 +21,11 @@ struct PairPosFormat2
   ValueFormat   valueFormat2;           /* ValueRecord definition--for the
                                          * second glyph of the pair--may be
                                          * zero (0) */
-  Offset16To<ClassDef>
+  typename Types::template OffsetTo<ClassDef>
                 classDef1;              /* Offset to ClassDef table--from
                                          * beginning of PairPos subtable--for
                                          * the first glyph of the pair */
-  Offset16To<ClassDef>
+  typename Types::template OffsetTo<ClassDef>
                 classDef2;              /* Offset to ClassDef table--from
                                          * beginning of PairPos subtable--for
                                          * the second glyph of the pair */
@@ -36,7 +37,7 @@ struct PairPosFormat2
                                          * class1-major, class2-minor,
                                          * Each entry has value1 and value2 */
   public:
-  DEFINE_SIZE_ARRAY (16, values);
+  DEFINE_SIZE_ARRAY (10 + 3 * Types::size, values);
 
   bool sanitize (hb_sanitize_context_t *c) const
   {