diff --git a/src/calibre/gui2/actions/catalog.py b/src/calibre/gui2/actions/catalog.py
index ba3756003c..523184db2c 100644
--- a/src/calibre/gui2/actions/catalog.py
+++ b/src/calibre/gui2/actions/catalog.py
@@ -85,7 +85,7 @@ class GenerateCatalogAction(InterfaceAction):
             dynamic.set('catalogs_to_be_synced', sync)
         self.gui.status_bar.show_message(_('Catalog generated.'), 3000)
         self.gui.sync_catalogs()
-        if job.fmt not in ['EPUB','MOBI']:
+        if job.fmt not in {'EPUB','MOBI', 'AZW3'}:
             export_dir = choose_dir(self.gui, _('Export Catalog Directory'),
                     _('Select destination for %(title)s.%(fmt)s') % dict(
                         title=job.catalog_title, fmt=job.fmt.lower()))
diff --git a/src/calibre/gui2/catalog/catalog_epub_mobi.py b/src/calibre/gui2/catalog/catalog_epub_mobi.py
index 485f84a642..7468ed6f27 100644
--- a/src/calibre/gui2/catalog/catalog_epub_mobi.py
+++ b/src/calibre/gui2/catalog/catalog_epub_mobi.py
@@ -31,7 +31,7 @@ class PluginWidget(QWidget,Ui_Form):
     sync_enabled = True
 
     # Formats supported by this plugin
-    formats = set(['epub','mobi'])
+    formats = set(['azw3','epub','mobi'])
 
     def __init__(self, parent=None):
         QWidget.__init__(self, parent)
@@ -872,7 +872,6 @@ class PrefixRules(GenericRulesTable):
             ('Math plus circled',u'\u2295'),
             ('Math times circled',u'\u2297'),
             ('Math times',u'\u00d7'),
-            ('O slash',u'\u00d8'),
             ('Paragraph',u'\u00b6'),
             ('Percent',u'%'),
             ('Plus-or-minus',u'\u00b1'),
diff --git a/src/calibre/library/catalogs/epub_mobi.py b/src/calibre/library/catalogs/epub_mobi.py
index 385a699c7b..1007c6d762 100644
--- a/src/calibre/library/catalogs/epub_mobi.py
+++ b/src/calibre/library/catalogs/epub_mobi.py
@@ -25,7 +25,7 @@ class EPUB_MOBI(CatalogPlugin):
     minimum_calibre_version = (0, 7, 40)
     author = 'Greg Riker'
     version = (1, 0, 0)
-    file_types = set(['epub','mobi'])
+    file_types = set(['azw3','epub','mobi'])
 
     THUMB_SMALLEST = "1.0"
     THUMB_LARGEST = "2.0"
diff --git a/src/calibre/library/catalogs/epub_mobi_builder.py b/src/calibre/library/catalogs/epub_mobi_builder.py
index 825778f0d5..91856600d8 100644
--- a/src/calibre/library/catalogs/epub_mobi_builder.py
+++ b/src/calibre/library/catalogs/epub_mobi_builder.py
@@ -1337,7 +1337,7 @@ Author '{0}':
                     pBookTag['class'] = "line_item"
                     ptc = 0
 
-                    pBookTag.insert(ptc, self.formatPrefix(book['prefix'],soup))
+                    pBookTag.insert(ptc, self.formatPrefix(new_entry['prefix'],soup))
                     ptc += 1
 
                     spanTag = Tag(soup, "span")