diff --git a/generators/async-file-system.js b/generators/async-file-system.js
index 391ecae2..13497096 100644
--- a/generators/async-file-system.js
+++ b/generators/async-file-system.js
@@ -43,7 +43,7 @@ async function *randomFileContents() {
         let result = new ArrayBuffer(numBytes);
         let view = new Uint8Array(result);
         for (let i = 0; i < numBytes; ++i)
-            view[i] = (i + counter) % 255;
+            view[i] = (i + counter) % 256;
         yield new DataView(result);
     }
 }
diff --git a/generators/sync-file-system.js b/generators/sync-file-system.js
index 126b2660..62c1159c 100644
--- a/generators/sync-file-system.js
+++ b/generators/sync-file-system.js
@@ -43,7 +43,7 @@ function *randomFileContents() {
         let result = new ArrayBuffer(numBytes);
         let view = new Uint8Array(result);
         for (let i = 0; i < numBytes; ++i)
-            view[i] = (i + counter) % 255;
+            view[i] = (i + counter) % 256;
         yield new DataView(result);
     }
 };