diff --git a/copyparty/web/up2k.js b/copyparty/web/up2k.js
index a05e414b..f645c6ce 100644
--- a/copyparty/web/up2k.js
+++ b/copyparty/web/up2k.js
@@ -21,6 +21,8 @@ var up2k = null,
     m = 'will use ' + sha_js + ' instead of native sha512 due to';
 
 try {
+    if (sread('nosubtle') || window.nosubtle)
+        throw 'chickenbit';
     var cf = crypto.subtle || crypto.webkitSubtle;
     cf.digest('SHA-512', new Uint8Array(1)).then(
         function (x) { console.log('sha-ok'); up2k = up2k_init(cf); },
@@ -1358,6 +1360,10 @@ function up2k_init(subtle) {
             for (var a = 0; a < Math.min(navigator.hardwareConcurrency || 4, 16); a++)
                 hws.push(new Worker(SR + '/.cpr/w.hash.js?_=' + TS));
 
+            if (!subtle)
+                for (var a = 0; a < hws.length; a++)
+                    hws[a].postMessage('nosubtle');
+
             console.log(hws.length + " hashers");
         }
 
@@ -2579,7 +2585,7 @@ function up2k_init(subtle) {
             nparts = upt.nparts,
             pcar = nparts[0],
             pcdr = nparts[nparts.length - 1],
-            maxsz = u2sz_max * 1024 * 1024;
+            maxsz = (u2sz_max > 1 ? u2sz_max : 2040) * 1024 * 1024;
 
         if (t.done)
             return console.log('done; skip chunk', t.name, t);
diff --git a/copyparty/web/w.hash.js b/copyparty/web/w.hash.js
index 98b8f01e..559e5957 100644
--- a/copyparty/web/w.hash.js
+++ b/copyparty/web/w.hash.js
@@ -20,6 +20,7 @@ catch (ex) {
 function load_fb() {
     subtle = null;
     importScripts('deps/sha512.hw.js');
+    console.log('using fallback hasher');
 }
 
 
@@ -29,6 +30,9 @@ var reader = null,
 
 
 onmessage = (d) => {
+    if (d.data == 'nosubtle')
+        return load_fb();
+
     if (busy)
         return postMessage(["panic", 'worker got another task while busy']);