diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 07744aefbe57d9838722a36bc7fbd680d00b2f3f..a11d5dcc549789d0b4e77e971fdf3c3bf4521f7b 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -2612,6 +2612,23 @@ struct Extension
  * GSUB/GPOS Common
  */
 
+struct hb_ot_layout_lookup_accelerator_t
+{
+  template <typename TLookup>
+  inline void init (const TLookup &lookup)
+  {
+    digest.init ();
+    lookup.add_coverage (&digest);
+  }
+  inline void fini (void) {}
+
+  inline bool may_have (hb_codepoint_t g) const
+  { return digest.may_have (g); }
+
+  private:
+  hb_set_digest_t digest;
+};
+
 struct GSUBGPOS
 {
   inline bool has_data (void) const { return version.to_int () != 0; }
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index fc83873ceb5096f4240411323e53d2b433595811..572e4cb927f8a31698f39ccb5acb950419b61856 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1094,7 +1094,7 @@ struct GSUBProxy
     accels (hb_ot_face_data (face)->GSUB->accels) {}
 
   const OT::GSUB &table;
-  const hb_ot_layout_lookup_accelerator_t *accels;
+  const OT::hb_ot_layout_lookup_accelerator_t *accels;
 };
 
 struct GPOSProxy
@@ -1108,13 +1108,13 @@ struct GPOSProxy
     accels (hb_ot_face_data (face)->GPOS->accels) {}
 
   const OT::GPOS &table;
-  const hb_ot_layout_lookup_accelerator_t *accels;
+  const OT::hb_ot_layout_lookup_accelerator_t *accels;
 };
 
 
 static inline bool
 apply_forward (OT::hb_ot_apply_context_t *c,
-	       const hb_ot_layout_lookup_accelerator_t &accel,
+	       const OT::hb_ot_layout_lookup_accelerator_t &accel,
 	       const OT::hb_get_subtables_context_t::array_t &subtables)
 {
   bool ret = false;
@@ -1144,7 +1144,7 @@ apply_forward (OT::hb_ot_apply_context_t *c,
 
 static inline bool
 apply_backward (OT::hb_ot_apply_context_t *c,
-	       const hb_ot_layout_lookup_accelerator_t &accel,
+	       const OT::hb_ot_layout_lookup_accelerator_t &accel,
 	       const OT::hb_get_subtables_context_t::array_t &subtables)
 {
   bool ret = false;
@@ -1174,7 +1174,7 @@ template <typename Proxy>
 static inline void
 apply_string (OT::hb_ot_apply_context_t *c,
 	      const typename Proxy::Lookup &lookup,
-	      const hb_ot_layout_lookup_accelerator_t &accel)
+	      const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   hb_buffer_t *buffer = c->buffer;
 
@@ -1270,7 +1270,7 @@ void hb_ot_map_t::position (const hb_ot_shape_plan_t *plan, hb_font_t *font, hb_
 void
 hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
 				const OT::SubstLookup &lookup,
-				const hb_ot_layout_lookup_accelerator_t &accel)
+				const OT::hb_ot_layout_lookup_accelerator_t &accel)
 {
   apply_string<GSUBProxy> (c, lookup, accel);
 }
diff --git a/src/hb-ot-layout.hh b/src/hb-ot-layout.hh
index f5ffe3112c37aadbffde5916b3ffb8ecb5b75daf..64b3d7480d67b2466ab10a133f9dfc0592d11349 100644
--- a/src/hb-ot-layout.hh
+++ b/src/hb-ot-layout.hh
@@ -112,32 +112,16 @@ hb_ot_layout_substitute_start (hb_font_t    *font,
 			       hb_buffer_t  *buffer);
 
 
-struct hb_ot_layout_lookup_accelerator_t
-{
-  template <typename TLookup>
-  inline void init (const TLookup &lookup)
-  {
-    digest.init ();
-    lookup.add_coverage (&digest);
-  }
-  inline void fini (void) {}
-
-  inline bool may_have (hb_codepoint_t g) const
-  { return digest.may_have (g); }
-
-  private:
-  hb_set_digest_t digest;
-};
-
 namespace OT {
   struct hb_ot_apply_context_t;
   struct SubstLookup;
+  struct hb_ot_layout_lookup_accelerator_t;
 }
 
 HB_INTERNAL void
 hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
 				const OT::SubstLookup &lookup,
-				const hb_ot_layout_lookup_accelerator_t &accel);
+				const OT::hb_ot_layout_lookup_accelerator_t &accel);
 
 
 /* Should be called before all the position_lookup's are done. */
diff --git a/src/hb-ot-shape-complex-arabic-fallback.hh b/src/hb-ot-shape-complex-arabic-fallback.hh
index 0ef60f64347f669b7f0e26b0cf8a686d5d251876..2aa0367280a99d03da82d47d425237bedc1576ae 100644
--- a/src/hb-ot-shape-complex-arabic-fallback.hh
+++ b/src/hb-ot-shape-complex-arabic-fallback.hh
@@ -201,7 +201,7 @@ struct arabic_fallback_plan_t
 
   hb_mask_t mask_array[ARABIC_FALLBACK_MAX_LOOKUPS];
   OT::SubstLookup *lookup_array[ARABIC_FALLBACK_MAX_LOOKUPS];
-  hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
+  OT::hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
 };
 
 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(HB_NO_WIN1256)