diff --git a/src/calibre/gui2/actions/add.py b/src/calibre/gui2/actions/add.py
index 8c7ea97104..ecbb5e6e2b 100644
--- a/src/calibre/gui2/actions/add.py
+++ b/src/calibre/gui2/actions/add.py
@@ -370,7 +370,7 @@ class AddAction(InterfaceAction):
                     accept = True
                     db.set_cover(cid, pmap)
                     cover_changed = True
-            elif ext in BOOK_EXTENSIONS:
+            else:
                 formats.append((ext, path))
                 accept = True
         if accept and event is not None:
diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index 86b754eab7..1b53973435 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -619,7 +619,7 @@ class BookDetails(QWidget):  # {{{
 
     def dragEnterEvent(self, event):
         md = event.mimeData()
-        if dnd_has_extension(md, self.DROPABBLE_EXTENSIONS) or \
+        if dnd_has_extension(md, self.DROPABBLE_EXTENSIONS, allow_all_extensions=True) or \
                 dnd_has_image(md):
             event.acceptProposedAction()
 
@@ -642,7 +642,7 @@ class BookDetails(QWidget):  # {{{
                 return
 
         # Now look for ebook files
-        urls, filenames = dnd_get_files(md, BOOK_EXTENSIONS)
+        urls, filenames = dnd_get_files(md, BOOK_EXTENSIONS, allow_all_extensions=True)
         if not urls:
             # Nothing found
             return
diff --git a/src/calibre/gui2/dnd.py b/src/calibre/gui2/dnd.py
index 245e87129f..01f4a356e9 100644
--- a/src/calibre/gui2/dnd.py
+++ b/src/calibre/gui2/dnd.py
@@ -158,7 +158,7 @@ def remote_urls_from_qurl(qurls, allowed_exts):
                 qurl.path())[1][1:].lower() in allowed_exts:
             yield bytes(qurl.toEncoded()), posixpath.basename(qurl.path())
 
-def dnd_has_extension(md, extensions):
+def dnd_has_extension(md, extensions, allow_all_extensions=False):
     if DEBUG:
         prints('\nDebugging DND event')
         for f in md.formats():
@@ -177,6 +177,8 @@ def dnd_has_extension(md, extensions):
         prints('Paths:', paths)
         prints('Extensions:', exts)
 
+    if allow_all_extensions:
+        return bool(exts)
     return bool(exts.intersection(frozenset(extensions)))
 
 def dnd_get_image(md, image_exts=IMAGE_EXTENSIONS):
@@ -236,7 +238,7 @@ def dnd_get_image(md, image_exts=IMAGE_EXTENSIONS):
 
     return None, None
 
-def dnd_get_files(md, exts):
+def dnd_get_files(md, exts, allow_all_extensions=False):
     '''
     Get the file in the QMimeData object md with an extension that is one of
     the extensions in exts.
@@ -249,9 +251,12 @@ def dnd_get_files(md, exts):
     urls = urls_from_md(md)
     # First look for a local file
     local_files = [path_from_qurl(x) for x in urls]
-    local_files = [p for p in local_files if
-            posixpath.splitext(urllib.unquote(p))[1][1:].lower() in
-            exts]
+    def is_ok(path):
+        ext = posixpath.splitext(path)[1][1:].lower()
+        if allow_all_extensions and ext:
+            return True
+        return ext in exts
+    local_files = [p for p in local_files if is_ok(urllib.unquote(p))]
     local_files = [x for x in local_files if os.path.exists(x)]
     if local_files:
         return local_files, None
diff --git a/src/calibre/gui2/widgets.py b/src/calibre/gui2/widgets.py
index 85b649109b..7ff14d2f56 100644
--- a/src/calibre/gui2/widgets.py
+++ b/src/calibre/gui2/widgets.py
@@ -177,14 +177,14 @@ class FormatList(QListWidget):  # {{{
 
     def dragEnterEvent(self, event):
         md = event.mimeData()
-        if dnd_has_extension(md, self.DROPABBLE_EXTENSIONS):
+        if dnd_has_extension(md, self.DROPABBLE_EXTENSIONS, allow_all_extensions=True):
             event.acceptProposedAction()
 
     def dropEvent(self, event):
         event.setDropAction(Qt.CopyAction)
         md = event.mimeData()
         # Now look for ebook files
-        urls, filenames = dnd_get_files(md, self.DROPABBLE_EXTENSIONS)
+        urls, filenames = dnd_get_files(md, self.DROPABBLE_EXTENSIONS, allow_all_extensions=True)
         if not urls:
             # Nothing found
             return