diff --git a/lib/font/cmap_build_subtables.js b/lib/font/cmap_build_subtables.js
index c80a219..2e72a2f 100644
--- a/lib/font/cmap_build_subtables.js
+++ b/lib/font/cmap_build_subtables.js
@@ -47,7 +47,7 @@ module.exports = function cmap_split(all_codepoints) {
       let prev_dist = (j - 1 >= 0) ? min_paths[j - 1].dist : 0;
       let s;
 
-      if (all_codepoints[i] - all_codepoints[j] < 256) {
+      if (all_codepoints[i] - all_codepoints[j] < 255) {
         s = estimate_format0_size(all_codepoints[j], all_codepoints[i]);
 
         /* eslint-disable max-depth */
@@ -61,7 +61,7 @@ module.exports = function cmap_split(all_codepoints) {
         }
       }
 
-      if (all_codepoints[i] - all_codepoints[j] < 256 && all_codepoints[i] - i === all_codepoints[j] - j) {
+      if (all_codepoints[i] - all_codepoints[j] < 255 && all_codepoints[i] - i === all_codepoints[j] - j) {
         s = estimate_format0_tiny_size(all_codepoints[j], all_codepoints[i]);
 
         /* eslint-disable max-depth */