diff --git a/customize.dist/login.js b/customize.dist/login.js
index e2148f5fe..d34395e52 100644
--- a/customize.dist/login.js
+++ b/customize.dist/login.js
@@ -47,7 +47,7 @@ define([
         var edSeed = opt.edSeed = dispense(32);
 
         // 64 more bytes to seed an additional signing key
-        opt.blockSeed = dispense(64);
+        opt.blockSeed = new Uint8Array(dispense(64));
 
         var blockKeys = opt.blockKeys = Block.genkeys(opt.blockSeed);
         opt.blockHash = Block.getBlockHash(blockKeys);
diff --git a/www/common/outer/login-block.js b/www/common/outer/login-block.js
index f56dbf907..36f387bdd 100644
--- a/www/common/outer/login-block.js
+++ b/www/common/outer/login-block.js
@@ -23,6 +23,9 @@ define([
 
     // should be deterministic from a seed...
     Block.genkeys = function (seed) {
+        if (!(seed instanceof Uint8Array)) {
+            throw new Error('INVALID_SEED_FORMAT');
+        }
         if (!seed || typeof(seed.length) !== 'number' || seed.length < 64) {
             throw new Error('INVALID_SEED_LENGTH');
         }