diff --git a/src/calibre/customize/builtins.py b/src/calibre/customize/builtins.py
index d91fc97a1d..af5590cc53 100644
--- a/src/calibre/customize/builtins.py
+++ b/src/calibre/customize/builtins.py
@@ -259,7 +259,7 @@ class LRXMetadataReader(MetadataReaderPlugin):
 class MOBIMetadataReader(MetadataReaderPlugin):
 
     name        = 'Read MOBI metadata'
-    file_types  = set(['mobi', 'prc', 'azw', 'azw4', 'pobi'])
+    file_types  = set(['mobi', 'prc', 'azw', 'azw3', 'azw4', 'pobi'])
     description = _('Read metadata from %s files')%'MOBI'
 
     def get_metadata(self, stream, ftype):
diff --git a/src/calibre/ebooks/__init__.py b/src/calibre/ebooks/__init__.py
index 82e8c6f925..09cc2fbaaf 100644
--- a/src/calibre/ebooks/__init__.py
+++ b/src/calibre/ebooks/__init__.py
@@ -31,7 +31,7 @@ BOOK_EXTENSIONS = ['lrf', 'rar', 'zip', 'rtf', 'lit', 'txt', 'txtz', 'text', 'ht
                    'epub', 'fb2', 'djv', 'djvu', 'lrx', 'cbr', 'cbz', 'cbc', 'oebzip',
                    'rb', 'imp', 'odt', 'chm', 'tpz', 'azw1', 'pml', 'pmlz', 'mbp', 'tan', 'snb',
                    'xps', 'oxps', 'azw4', 'book', 'zbf', 'pobi', 'docx', 'md',
-                   'textile', 'markdown', 'ibook', 'iba']
+                   'textile', 'markdown', 'ibook', 'iba', 'azw3']
 
 class HTMLRenderer(object):
 
diff --git a/src/calibre/ebooks/conversion/plugins/mobi_input.py b/src/calibre/ebooks/conversion/plugins/mobi_input.py
index 0e12dd5db7..3817a7bda9 100644
--- a/src/calibre/ebooks/conversion/plugins/mobi_input.py
+++ b/src/calibre/ebooks/conversion/plugins/mobi_input.py
@@ -28,7 +28,7 @@ class MOBIInput(InputFormatPlugin):
     name        = 'MOBI Input'
     author      = 'Kovid Goyal'
     description = 'Convert MOBI files (.mobi, .prc, .azw) to HTML'
-    file_types  = set(['mobi', 'prc', 'azw'])
+    file_types  = set(['mobi', 'prc', 'azw', 'azw3'])
 
     def convert(self, stream, options, file_ext, log,
                 accelerators):