diff --git a/doc/notes.txt b/doc/notes.txt
index a7205bf5..af6b0df9 100644
--- a/doc/notes.txt
+++ b/doc/notes.txt
@@ -155,6 +155,7 @@ TODO:
   - allow text/binary change
   - importing from subtree commits to root anyway
   - publishing Markdown file loads default file? 
+  - better text/binary detection (e.g. 0xa9 copyright)
 - keyboard shortcuts
   - ctrl+alt+l on ubuntu locks screen
   - alt-D doesn't work anymore
diff --git a/src/common/util.ts b/src/common/util.ts
index a95b35ce..ec27d6a5 100644
--- a/src/common/util.ts
+++ b/src/common/util.ts
@@ -339,12 +339,10 @@ export function isProbablyBinary(path:string, data?:number[] | Uint8Array) : boo
       if ((c & 0xe0) == 0xc0) nextra = 1;
       else if ((c & 0xf0) == 0xe0) nextra = 2;
       else if ((c & 0xf8) == 0xf0) nextra = 3;
-      else {
-        score++;
-        break;
-      }
+      else if (c < 0xa0) score++;
+      else if (c == 0xff) score++;
       while (nextra--) {
-        if ((data[i++] & 0xc0) != 0x80) {
+        if (i >= data.length || (data[i++] & 0xc0) != 0x80) {
           score++;
           break;
         }
diff --git a/src/ide/ui.ts b/src/ide/ui.ts
index f467fa13..ef5fa49b 100644
--- a/src/ide/ui.ts
+++ b/src/ide/ui.ts
@@ -88,7 +88,10 @@ function gaEvent(category:string, action:string, label?:string, value?:string) {
 function alertError(s:string) {
   gaEvent('error', platform_id||'error', s);
   setWaitDialog(false);
-  bootbox.alert(s);
+  bootbox.alert({
+    title: '<span class="glyphicon glyphicon-alert" aria-hidden="true"></span> Alert',
+    message: s
+  });
 }
 function alertInfo(s:string) {
   setWaitDialog(false);
@@ -129,11 +132,11 @@ function requestPersistPermission(interactive: boolean, failureonly: boolean) {
       if (persistent) {
         interactive && !failureonly && alertInfo("Your browser says it will persist your local file edits, but you may want to back up your work anyway.");
       } else {
-        interactive && alertInfo("Your browser refused to expand the peristent storage quota. Your edits may not be preserved after closing the page.");
+        interactive && alertError("Your browser refused to expand the peristent storage quota. Your edits may not be preserved after closing the page.");
       }
     });
   } else {
-    interactive && alertInfo("Your browser doesn't support expanding the persistent storage quota. Your edits may not be preserved after closing the page.");
+    interactive && alertError("Your browser doesn't support expanding the persistent storage quota. Your edits may not be preserved after closing the page.");
   }
 }
 
diff --git a/test/cli/testutil.js b/test/cli/testutil.js
index ba254aa5..734657b2 100644
--- a/test/cli/testutil.js
+++ b/test/cli/testutil.js
@@ -121,5 +121,10 @@ describe('string functions', function() {
     assert.ok(util.isProbablyBinary('test.chr'));
     assert.ok(!util.isProbablyBinary('test.txt'));
     assert.ok(util.isProbablyBinary('test.dat'));
+    assert.ok(!util.isProbablyBinary(null, [0x20,0xa9,0x20,0x31,0x39,0x38,0x32]));
+    assert.ok(util.isProbablyBinary(null, [0x00,0x00])); // 00 is binary
+    assert.ok(util.isProbablyBinary(null, [0x9f])); // 9f is binary
+    assert.ok(util.isProbablyBinary(null, [0xff])); // FF is binary
+    assert.ok(util.isProbablyBinary(null, [0xf0,0x12])); // ran out of data
   });
 });