diff --git a/src/calibre/srv/utils.py b/src/calibre/srv/utils.py
index 1c4b891e11..63765cd969 100644
--- a/src/calibre/srv/utils.py
+++ b/src/calibre/srv/utils.py
@@ -466,3 +466,6 @@ class ReadOnlyFileBuffer(object):
     def getvalue(self):
         return self.mv
 
+    def close(self):
+        pass
+
diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index d0799cf96f..a7208699f6 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -12,8 +12,10 @@ __docformat__ = 'restructuredtext en'
 Test a binary calibre build to ensure that all needed binary images/libraries have loaded.
 '''
 
-import cStringIO, os, ctypes
+import cStringIO, os, ctypes, shutil
+from calibre import CurrentDir
 from calibre.constants import plugins, iswindows, islinux, isosx
+from calibre.ptempfile import TemporaryDirectory
 
 def test_dlls():
     import win32api
@@ -239,10 +241,27 @@ def test_markdown():
     sanitize_html(b'''<script>moo</script>xxx<img src="http://moo.com/x.jpg">''')
     print('Markdown OK!')
 
+def test_image_compression():
+    from calibre.utils.img import optimize_png, optimize_jpeg, encode_jpeg
+    with TemporaryDirectory() as tdir, CurrentDir(tdir):
+        shutil.copyfile(I('devices/kindle.jpg'), 'test.jpg')
+        ret = optimize_jpeg('test.jpg')
+        if ret is not None:
+            raise SystemExit(ret)
+        ret = encode_jpeg('test.jpg')
+        if ret is not None:
+            raise SystemExit(ret)
+        shutil.copyfile(I('lt.png'), 'test.png')
+        ret = optimize_png('test.png')
+        if ret is not None:
+            raise SystemExit(ret)
+    print('Image compression OK!')
+
 def test():
     if iswindows:
         test_dlls()
     test_plugins()
+    test_image_compression()
     test_lzma()
     test_dukpy()
     test_spell()
diff --git a/src/calibre/utils/img.py b/src/calibre/utils/img.py
index bd91b64f38..5a1426505d 100644
--- a/src/calibre/utils/img.py
+++ b/src/calibre/utils/img.py
@@ -98,7 +98,7 @@ def run_optimizer(file_path, cmd, as_filter=False, input_data=None):
             inw = Thread(name='CopyInput', target=copy, args=(src, p.stdin))
             inw.daemon = True
             inw.start()
-            outw = Thread('CopyOutput', target=copy, args=(p.stdout, outf))
+            outw = Thread(name='CopyOutput', target=copy, args=(p.stdout, outf))
             outw.daemon = True
             outw.start()
         raw = force_unicode(stderr.read())
@@ -137,4 +137,4 @@ def encode_jpeg(file_path, quality=80):
     buf.open(QBuffer.WriteOnly)
     if not img.save(buf, 'PPM'):
         raise ValueError('Failed to export image to PPM')
-    return run_optimizer(file_path, cmd, as_filter=True, input_data=ReadOnlyFileBuffer(ba.data))
+    return run_optimizer(file_path, cmd, as_filter=True, input_data=ReadOnlyFileBuffer(ba.data()))