diff --git a/setup/gui.py b/setup/gui.py
index 1c9c5aefd9..4b6a86126e 100644
--- a/setup/gui.py
+++ b/setup/gui.py
@@ -58,7 +58,7 @@ class GUI(Command):
                 for s in sources:
                     files.append('<file>%s</file>'%s)
                 manifest = '<RCC>\n<qresource prefix="/">\n%s\n</qresource>\n</RCC>'%'\n'.join(sorted(files))
-                with open('images.qrc', 'wb') as f:
+                with open('images.qrc', 'w') as f:
                     f.write(manifest)
         finally:
             os.chdir(cwd)
diff --git a/src/calibre/gui2/__init__.py b/src/calibre/gui2/__init__.py
index d16d949c43..1f5325d8d5 100644
--- a/src/calibre/gui2/__init__.py
+++ b/src/calibre/gui2/__init__.py
@@ -1288,7 +1288,7 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
         if force_compile or not os.path.exists(compiled_form) or os.stat(form).st_mtime > os.stat(compiled_form).st_mtime:
             if not summary:
                 info('\tCompiling form', form)
-            buf = io.BytesIO()
+            buf = io.StringIO()
             compileUi(form, buf)
             dat = buf.getvalue()
             dat = dat.replace('import images_rc', '')
@@ -1298,7 +1298,7 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
             dat = dat.replace('_("d MMM yyyy")', '"d MMM yyyy"')
             dat = pat.sub(sub, dat)
 
-            open(compiled_form, 'wb').write(dat)
+            open(compiled_form, 'w').write(dat)
             num += 1
     if num:
         info('Compiled %d forms' % num)