diff --git a/src/hb-subset-plan-layout.cc b/src/hb-subset-plan-layout.cc
index c0c20f094..aa2807b69 100644
--- a/src/hb-subset-plan-layout.cc
+++ b/src/hb-subset-plan-layout.cc
@@ -35,6 +35,25 @@ using OT::Layout::GPOS;
 
 #ifndef HB_NO_SUBSET_LAYOUT
 
+void
+remap_used_mark_sets (hb_subset_plan_t *plan,
+                      hb_map_t& used_mark_sets_map)
+{
+  hb_blob_ptr_t<OT::GDEF> gdef = plan->source_table<OT::GDEF> ();
+
+  if (!gdef->has_data () || !gdef->has_mark_glyph_sets ())
+  {
+    gdef.destroy ();
+    return;
+  }
+
+  hb_set_t used_mark_sets;
+  gdef->get_mark_glyph_sets ().collect_used_mark_sets (plan->_glyphset_gsub, used_mark_sets);
+  gdef.destroy ();
+
+  remap_indexes (&used_mark_sets, &used_mark_sets_map);
+}
+
 /*
  * Removes all tags from 'tags' that are not in filter. Additionally eliminates any duplicates.
  * Returns true if anything was removed (not including duplicates).
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index 45dd84e80..dc344fabb 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -33,7 +33,7 @@
 #include "hb-ot-cmap-table.hh"
 #include "hb-ot-glyf-table.hh"
 #include "hb-ot-layout-base-table.hh"
-#include "hb-ot-layout-gdef-table.hh"
+//#include "hb-ot-layout-gdef-table.hh"
 #include "hb-ot-cff1-table.hh"
 #include "hb-ot-cff2-table.hh"
 #include "OT/Color/COLR/COLR.hh"
@@ -337,25 +337,6 @@ _math_closure (hb_subset_plan_t *plan,
   math.destroy ();
 }
 
-static inline void
-_remap_used_mark_sets (hb_subset_plan_t *plan,
-                       hb_map_t& used_mark_sets_map)
-{
-  hb_blob_ptr_t<OT::GDEF> gdef = plan->source_table<OT::GDEF> ();
-
-  if (!gdef->has_data () || !gdef->has_mark_glyph_sets ())
-  {
-    gdef.destroy ();
-    return;
-  }
-
-  hb_set_t used_mark_sets;
-  gdef->get_mark_glyph_sets ().collect_used_mark_sets (plan->_glyphset_gsub, used_mark_sets);
-  gdef.destroy ();
-
-  remap_indexes (&used_mark_sets, &used_mark_sets_map);
-}
-
 static inline void
 _remove_invalid_gids (hb_set_t *glyphs,
 		      unsigned int num_glyphs)
@@ -1055,8 +1036,10 @@ hb_subset_plan_t::hb_subset_plan_t (hb_face_t *face,
   for (auto &v : bounds_height_vec)
     v = 0xFFFFFFFF;
 
+#ifndef HB_NO_SUBSET_LAYOUT    
   if (!drop_tables.has (HB_OT_TAG_GDEF))
-    _remap_used_mark_sets (this, used_mark_sets_map);
+    remap_used_mark_sets (this, used_mark_sets_map);
+#endif
 
 #ifndef HB_NO_VAR
 #ifndef HB_NO_BASE
diff --git a/src/hb-subset-plan.hh b/src/hb-subset-plan.hh
index e358cb3bc..b1a67b40b 100644
--- a/src/hb-subset-plan.hh
+++ b/src/hb-subset-plan.hh
@@ -296,14 +296,21 @@ struct hb_subset_plan_t
   }
 };
 
-void
+// hb-subset-plan implementation is split into multiple files to keep
+// compile times more reasonable:
+// - hb-subset-plan.cc
+// - hb-subset-plan-layout.cc
+//
+// The functions below are those needed to connect the split files
+// above together.
+HB_INTERNAL void
 remap_indexes (const hb_set_t *indexes,
                hb_map_t       *mapping /* OUT */);
 
 
 #ifndef HB_NO_VAR
 template<typename ItemVarStore>
-void
+HB_INTERNAL void
 remap_variation_indices (const ItemVarStore &var_store,
                          const hb_set_t &variation_indices,
                          const hb_vector_t<int>& normalized_coords,
@@ -311,7 +318,7 @@ remap_variation_indices (const ItemVarStore &var_store,
                          bool no_variations, /* all axes pinned */
                          hb_hashmap_t<unsigned, hb_pair_t<unsigned, int>> &variation_idx_delta_map /* OUT */);
 
-void
+HB_INTERNAL void
 generate_varstore_inner_maps (const hb_set_t& varidx_set,
                               unsigned subtable_count,
                               hb_vector_t<hb_inc_bimap_t> &inner_maps /* OUT */);
@@ -320,14 +327,19 @@ generate_varstore_inner_maps (const hb_set_t& varidx_set,
 #ifndef HB_NO_SUBSET_LAYOUT
 typedef hb_hashmap_t<unsigned, hb::unique_ptr<hb_set_t>> script_langsys_map;
 
-void layout_nameid_closure (hb_subset_plan_t* plan,
-                            hb_set_t* drop_tables);
+HB_INTERNAL void
+remap_used_mark_sets (hb_subset_plan_t *plan,
+                      hb_map_t& used_mark_sets_map);
 
-void
+HB_INTERNAL void
+layout_nameid_closure (hb_subset_plan_t* plan,
+                       hb_set_t* drop_tables);
+
+HB_INTERNAL void
 layout_populate_gids_to_retain (hb_subset_plan_t* plan,
                                 hb_set_t* drop_tables);
 
-void
+HB_INTERNAL void
 collect_layout_variation_indices (hb_subset_plan_t* plan);
 #endif