diff --git a/protocol/src/test/typescript/zfoo/buffer/Longbits.ts b/protocol/src/test/typescript/zfoo/buffer/Longbits.ts
index a538cace..3bb8a20d 100644
--- a/protocol/src/test/typescript/zfoo/buffer/Longbits.ts
+++ b/protocol/src/test/typescript/zfoo/buffer/Longbits.ts
@@ -43,7 +43,7 @@ class Longbits {
   /**
    * Converts this long bits to a long.
    */
-  toLong(unsigned): Long {
+  toLong(unsigned: boolean): Long {
     return new Long(this.lo | 0, this.hi | 0, Boolean(unsigned));
   };