diff --git a/src/calibre/ebooks/oeb/polish/container.py b/src/calibre/ebooks/oeb/polish/container.py
index 34cfc12179..25e757ee07 100644
--- a/src/calibre/ebooks/oeb/polish/container.py
+++ b/src/calibre/ebooks/oeb/polish/container.py
@@ -998,6 +998,13 @@ def do_explode(path, dest):
             mr = Mobi8Reader(mr, default_log)
             opf = os.path.abspath(mr())
             obfuscated_fonts = mr.encrypted_fonts
+            # If there are no images then the azw3 input plugin dumps all
+            # binary records as .unknown images, remove them
+            if os.path.exists('images') and os.path.isdir('images'):
+                files = os.listdir('images')
+                unknown = [x for x in files if x.endswith('.unknown')]
+                if len(files) == len(unknown):
+                    [os.remove('images/'+f) for f in files]
             try:
                 os.remove('debug-raw.html')
             except: