diff --git a/src/calibre/devices/usbms/books.py b/src/calibre/devices/usbms/books.py
index d065d0f47a..be154f35c1 100644
--- a/src/calibre/devices/usbms/books.py
+++ b/src/calibre/devices/usbms/books.py
@@ -47,7 +47,7 @@ class Book(MetaInformation):
 
     def __eq__(self, other):
         # use lpath because the prefix can change, changing path
-        return self.path == getattr(other, 'lpath', None)
+        return self.lpath == getattr(other, 'lpath', None)
 
     @dynamic_property
     def db_id(self):
diff --git a/src/calibre/gui2/custom_column_widgets.py b/src/calibre/gui2/custom_column_widgets.py
index de9d839684..90ac7dbbaf 100644
--- a/src/calibre/gui2/custom_column_widgets.py
+++ b/src/calibre/gui2/custom_column_widgets.py
@@ -101,6 +101,11 @@ class Float(Int):
         w.setSpecialValueText(_('Undefined'))
         w.setSingleStep(1)
 
+    def setter(self, val):
+        if val is None:
+            val = self.widgets[1].minimum()
+        self.widgets[1].setValue(val)
+
 class Rating(Int):
 
     def setup_ui(self, parent):
diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 7b98dc4537..31e9b43f86 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -1304,12 +1304,6 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                 aid = self.conn.execute('INSERT INTO series(name) VALUES (?)', (series,)).lastrowid
             self.conn.execute('INSERT INTO books_series_link(book, series) VALUES (?,?)', (id, aid))
         self.conn.commit()
-        try:
-            row = self.row(id)
-            if row is not None:
-                self.data.set(row, 9, series)
-        except ValueError:
-            pass
         self.data.set(id, self.FIELD_MAP['series'], series, row_is_id=True)
         if notify:
             self.notify('metadata', [id])