diff --git a/libass/ass_cache.h b/libass/ass_cache.h
index 7ff75885b8..89e69f783f 100644
--- a/libass/ass_cache.h
+++ b/libass/ass_cache.h
@@ -66,6 +66,7 @@ typedef struct glyph_hash_key_s {
 	int bold, italic;
 	unsigned scale_x, scale_y; // 16.16
 	FT_Vector advance; // subpixel shift vector
+	unsigned outline; // border width, 16.16
 } glyph_hash_key_t;
 
 typedef struct glyph_hash_val_s {
diff --git a/libass/ass_render.c b/libass/ass_render.c
index da4d98ae9e..63acb5bafa 100644
--- a/libass/ass_render.c
+++ b/libass/ass_render.c
@@ -1237,6 +1237,7 @@ static void get_outline_glyph(int symbol, glyph_info_t* info, FT_Vector* advance
 	key.advance = *advance;
 	key.bold = render_context.bold;
 	key.italic = render_context.italic;
+	key.outline = render_context.border * 0xFFFF;
 
 	info->glyph = info->outline_glyph = 0;