diff --git a/src/Makefile.sources b/src/Makefile.sources
index eb9cd36ab..5e1c4e4f6 100644
--- a/src/Makefile.sources
+++ b/src/Makefile.sources
@@ -190,6 +190,7 @@ HB_SUBSET_sources = \
 HB_SUBSET_headers = \
 	hb-subset.h \
 	hb-subset-plan.h \
+	hb-subset-private.hh \
 	$(NULL)
 
 HB_GOBJECT_sources = hb-gobject-structs.cc
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index 705c17f1c..7da9dae8f 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -40,7 +40,7 @@ struct hb_subset_plan_t {
  * to a provide profile and input. The plan describes
  * which tables and glyphs should be retained.
  *
- * Return value: New plan with default settings.
+ * Return value: New subset plan.
  *
  * Since: 1.7.5
  **/
diff --git a/src/hb-subset-private.hh b/src/hb-subset-private.hh
new file mode 100644
index 000000000..b38ab0b26
--- /dev/null
+++ b/src/hb-subset-private.hh
@@ -0,0 +1,40 @@
+/*
+ * Copyright © 2018  Google, Inc.
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ *
+ * Google Author(s): Garret Rieger
+ */
+
+#ifndef HB_SUBSET_PRIVATE_HH
+#define HB_SUBSET_PRIVATE_HH
+
+#include "hb-object-private.hh"
+#include "hb-private.hh"
+
+struct hb_subset_input_t {
+  hb_object_header_t header;
+  ASSERT_POD ();
+
+  hb_set_t *codepoints;
+};
+
+#endif /* HB_SUBSET_PRIVATE_HH */
diff --git a/src/hb-subset.cc b/src/hb-subset.cc
index f56217f67..fe821e0aa 100644
--- a/src/hb-subset.cc
+++ b/src/hb-subset.cc
@@ -25,23 +25,15 @@
  * Google Author(s): Garret Rieger, Rod Sheeter
  */
 
-#include "hb-private.hh"
-
 #include "hb-object-private.hh"
-
+#include "hb-private.hh"
+#include "hb-subset-private.hh"
 
 struct hb_subset_profile_t {
   hb_object_header_t header;
   ASSERT_POD ();
 };
 
-struct hb_subset_input_t {
-  hb_object_header_t header;
-  ASSERT_POD ();
-
-  hb_set_t *codepoints;
-};
-
 struct hb_subset_face_t {
   hb_object_header_t header;
   ASSERT_POD ();