diff --git a/src/hb-ot-layout-gsubgpos-private.hh b/src/hb-ot-layout-gsubgpos-private.hh
index 1390a2e..aeaaefa 100644
--- a/src/hb-ot-layout-gsubgpos-private.hh
+++ b/src/hb-ot-layout-gsubgpos-private.hh
@@ -835,7 +835,6 @@
     _hb_glyph_info_set_lig_props_for_ligature (&buffer->cur(), lig_id, total_component_count);
     if (_hb_glyph_info_get_general_category (&buffer->cur()) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK)
     {
-      _hb_glyph_info_set_modified_combining_class (&buffer->cur(), 0);
       _hb_glyph_info_set_general_category (&buffer->cur(), HB_UNICODE_GENERAL_CATEGORY_OTHER_LETTER);
     }
   }
diff --git a/src/hb-ot-layout-private.hh b/src/hb-ot-layout-private.hh
index 8e6164e..43a8bc1 100644
--- a/src/hb-ot-layout-private.hh
+++ b/src/hb-ot-layout-private.hh
@@ -258,7 +258,8 @@
 _hb_glyph_info_set_general_category (hb_glyph_info_t *info,
 				     hb_unicode_general_category_t gen_cat)
 {
-  info->unicode_props() = (unsigned int) gen_cat | (info->unicode_props() & ~UPROPS_MASK_GEN_CAT);
+  /* Clears top-byte. */
+  info->unicode_props() = (unsigned int) gen_cat | (info->unicode_props() & (0xFF & ~UPROPS_MASK_GEN_CAT));
 }
 
 static inline hb_unicode_general_category_t