diff --git a/src/harfbuzz-gpos-private.h b/src/harfbuzz-gpos-private.h
index ba08ecfea9224c9eef015cc15490a0643bd32a95..1bd6ec4f7b20817274900fdf73f3fc5563aad3bb 100644
--- a/src/harfbuzz-gpos-private.h
+++ b/src/harfbuzz-gpos-private.h
@@ -655,6 +655,19 @@ struct  HB_ChainContextPos_
 typedef struct HB_ChainContextPos_  HB_ChainContextPos;
 
 
+#if 0
+/* LookupType 10 */
+struct HB_ExtensionPos_
+{
+  FT_UShort      PosFormat;           /* always 1 */
+  FT_UShort      LookuptType;         /* lookup-type of referenced subtable */
+  HB_GPOS_SubTable *subtable;         /* referenced subtable */
+};
+
+typedef struct HB_ExtensionPos_  HB_ExtensionPos;
+#endif
+
+
 union  HB_GPOS_SubTable_
 {
   HB_SinglePos        single;
diff --git a/src/harfbuzz-gsub-private.h b/src/harfbuzz-gsub-private.h
index 7f339cdb92e2acb2adda3e20431511b917c98458..45bae945b3e2b1314abfceaa060de1067c438373 100644
--- a/src/harfbuzz-gsub-private.h
+++ b/src/harfbuzz-gsub-private.h
@@ -403,6 +403,19 @@ struct  HB_ChainContextSubst_
 typedef struct HB_ChainContextSubst_  HB_ChainContextSubst;
 
 
+#if 0
+/* LookupType 7 */
+struct HB_ExtensionSubst_
+{
+  FT_UShort      SubstFormat;         /* always 1 */
+  FT_UShort      LookuptType;         /* lookup-type of referenced subtable */
+  HB_GSUB_SubTable *subtable;         /* referenced subtable */
+};
+
+typedef struct HB_ExtensionSubst_  HB_ExtensionSubst;
+#endif
+
+
 /* LookupType 8 */
 struct HB_ReverseChainContextSubst_
 {