diff --git a/src/hb-ucdn.cc b/src/hb-ucdn.cc
index d8404b294..d41cf5b93 100644
--- a/src/hb-ucdn.cc
+++ b/src/hb-ucdn.cc
@@ -167,14 +167,16 @@ static const hb_script_t ucdn_script_translate[] =
 };
 
 static hb_unicode_combining_class_t
-hb_ucdn_combining_class(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+hb_ucdn_combining_class(hb_unicode_funcs_t *ufuncs HB_UNUSED,
+			hb_codepoint_t unicode,
 			void *user_data HB_UNUSED)
 {
     return (hb_unicode_combining_class_t) ucdn_get_combining_class(unicode);
 }
 
 static unsigned int
-hb_ucdn_eastasian_width(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+hb_ucdn_eastasian_width(hb_unicode_funcs_t *ufuncs HB_UNUSED,
+			hb_codepoint_t unicode,
 			void *user_data HB_UNUSED)
 {
     int w = ucdn_get_east_asian_width(unicode);
@@ -182,28 +184,31 @@ hb_ucdn_eastasian_width(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
 }
 
 static hb_unicode_general_category_t
-hb_ucdn_general_category(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+hb_ucdn_general_category(hb_unicode_funcs_t *ufuncs HB_UNUSED,
+			 hb_codepoint_t unicode,
 			 void *user_data HB_UNUSED)
 {
     return (hb_unicode_general_category_t)ucdn_get_general_category(unicode);
 }
 
 static hb_codepoint_t
-hb_ucdn_mirroring(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+hb_ucdn_mirroring(hb_unicode_funcs_t *ufuncs HB_UNUSED,
+		  hb_codepoint_t unicode,
 		  void *user_data HB_UNUSED)
 {
     return ucdn_mirror(unicode);
 }
 
 static hb_script_t
-hb_ucdn_script(hb_unicode_funcs_t *ufuncs, hb_codepoint_t unicode,
+hb_ucdn_script(hb_unicode_funcs_t *ufuncs HB_UNUSED,
+	       hb_codepoint_t unicode,
 	       void *user_data HB_UNUSED)
 {
     return ucdn_script_translate[ucdn_get_script(unicode)];
 }
 
 static hb_bool_t
-hb_ucdn_compose(hb_unicode_funcs_t *ufuncs,
+hb_ucdn_compose(hb_unicode_funcs_t *ufuncs HB_UNUSED,
 		hb_codepoint_t a, hb_codepoint_t b, hb_codepoint_t *ab,
 		void *user_data HB_UNUSED)
 {
@@ -211,7 +216,7 @@ hb_ucdn_compose(hb_unicode_funcs_t *ufuncs,
 }
 
 static hb_bool_t
-hb_ucdn_decompose(hb_unicode_funcs_t *ufuncs,
+hb_ucdn_decompose(hb_unicode_funcs_t *ufuncs HB_UNUSED,
 		  hb_codepoint_t ab, hb_codepoint_t *a, hb_codepoint_t *b,
 		  void *user_data HB_UNUSED)
 {
@@ -219,7 +224,7 @@ hb_ucdn_decompose(hb_unicode_funcs_t *ufuncs,
 }
 
 static unsigned int
-hb_ucdn_decompose_compatibility(hb_unicode_funcs_t *ufuncs,
+hb_ucdn_decompose_compatibility(hb_unicode_funcs_t *ufuncs HB_UNUSED,
 				hb_codepoint_t u, hb_codepoint_t *decomposed,
 				void *user_data HB_UNUSED)
 {