diff --git a/src/libs/ttffont.js b/src/libs/ttffont.js
index 8410b7d1a..f45145182 100644
--- a/src/libs/ttffont.js
+++ b/src/libs/ttffont.js
@@ -1579,7 +1579,7 @@ var CompoundGlyph = (function() {
     while (true) {
       flags = data.readShort();
       this.glyphOffsets.push(data.pos);
-      this.glyphIDs.push(data.readShort());
+      this.glyphIDs.push(data.readUInt16());
       if (!(flags & MORE_COMPONENTS)) {
         break;
       }