diff --git a/src/calibre/ebooks/html/input.py b/src/calibre/ebooks/html/input.py
index 69eb493c7d..f68ea4f678 100644
--- a/src/calibre/ebooks/html/input.py
+++ b/src/calibre/ebooks/html/input.py
@@ -11,7 +11,7 @@ __docformat__ = 'restructuredtext en'
 Input plugin for HTML or OPF ebooks.
 '''
 
-import os, re, sys, uuid, tempfile
+import os, re, sys, uuid, tempfile, errno
 from urlparse import urlparse, urlunparse
 from urllib import unquote
 from functools import partial
@@ -75,7 +75,7 @@ class IgnoreFile(Exception):
 
     def __init__(self, msg, errno):
         Exception.__init__(self, msg)
-        self.doesnt_exist = errno == 2
+        self.doesnt_exist = errno == errno.ENOENT
         self.errno = errno
 
 class HTMLFile(object):
diff --git a/src/calibre/ebooks/pdf/pdftohtml.py b/src/calibre/ebooks/pdf/pdftohtml.py
index a791dab48a..9d81c73c2a 100644
--- a/src/calibre/ebooks/pdf/pdftohtml.py
+++ b/src/calibre/ebooks/pdf/pdftohtml.py
@@ -53,7 +53,7 @@ def pdftohtml(output_dir, pdf_path, no_images):
             p = popen(cmd, stderr=logf._fd, stdout=logf._fd,
                     stdin=subprocess.PIPE)
         except OSError as err:
-            if err.errno == 2:
+            if err.errno == errno.ENOENT:
                 raise ConversionError(_('Could not find pdftohtml, check it is in your PATH'))
             else:
                 raise
diff --git a/src/calibre/gui2/metadata/basic_widgets.py b/src/calibre/gui2/metadata/basic_widgets.py
index a349b8ca92..fe20be765f 100644
--- a/src/calibre/gui2/metadata/basic_widgets.py
+++ b/src/calibre/gui2/metadata/basic_widgets.py
@@ -7,7 +7,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import textwrap, re, os
+import textwrap, re, os, errno
 
 from PyQt4.Qt import (Qt, QDateEdit, QDate, pyqtSignal, QMessageBox,
     QIcon, QToolButton, QWidget, QLabel, QGridLayout, QApplication,
@@ -98,7 +98,7 @@ class TitleEdit(EnLineEdit):
                 getattr(db, 'set_'+ self.TITLE_ATTR)(id_, title, notify=False,
                         commit=False)
         except (IOError, OSError) as err:
-            if getattr(err, 'errno', -1) == 13: # Permission denied
+            if getattr(err, 'errno', -1) == errno.EACCES: # Permission denied
                 import traceback
                 fname = err.filename if err.filename else 'file'
                 error_dialog(self, _('Permission denied'),
@@ -262,7 +262,7 @@ class AuthorsEdit(MultiCompleteComboBox):
             self.books_to_refresh |= db.set_authors(id_, authors, notify=False,
                 allow_case_change=True)
         except (IOError, OSError) as err:
-            if getattr(err, 'errno', -1) == 13: # Permission denied
+            if getattr(err, 'errno', -1) == errno.EACCES: # Permission denied
                 import traceback
                 fname = err.filename if err.filename else 'file'
                 error_dialog(self, _('Permission denied'),
diff --git a/src/calibre/gui2/metadata/single.py b/src/calibre/gui2/metadata/single.py
index a2666b0351..bbc5f6fce4 100644
--- a/src/calibre/gui2/metadata/single.py
+++ b/src/calibre/gui2/metadata/single.py
@@ -7,7 +7,7 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import os
+import os, errno
 from functools import partial
 
 from PyQt4.Qt import (Qt, QVBoxLayout, QHBoxLayout, QWidget, QPushButton,
@@ -427,7 +427,7 @@ class MetadataSingleDialogBase(ResizableDialog):
                 self.books_to_refresh |= getattr(widget, 'books_to_refresh',
                         set([]))
             except IOError as err:
-                if err.errno == 13: # Permission denied
+                if err.errno == errno.EACCES: # Permission denied
                     import traceback
                     fname = err.filename if err.filename else 'file'
                     error_dialog(self, _('Permission denied'),