diff --git a/src/calibre/devices/prst1/driver.py b/src/calibre/devices/prst1/driver.py
index dba611d82c..6e231a0d1c 100644
--- a/src/calibre/devices/prst1/driver.py
+++ b/src/calibre/devices/prst1/driver.py
@@ -268,42 +268,42 @@ class PRST1(USBMS):
         collections = booklist.get_collections(collections_attributes)
 
         with closing(sqlite.connect(dbpath)) as connection:
-			self.remove_orphaned_records(connection, dbpath)
+            self.remove_orphaned_records(connection, dbpath)
             self.update_device_books(connection, booklist, source_id,
                     plugboard, dbpath)
             self.update_device_collections(connection, booklist, collections, source_id, dbpath)
 
         debug_print('PRST1: finished update_device_database')
 
-	def remove_orphaned_records(self, connection, dbpath):
-		from sqlite3 import DatabaseError
+    def remove_orphaned_records(self, connection, dbpath):
+        from sqlite3 import DatabaseError
 
         try:
-			cursor = connection.cursor()
-		
-			debug_print("Removing Orphaned Collection Records")
-		
-			# Purge any collections references that point into the abyss
-			query = 'DELETE FROM collections WHERE content_id NOT IN (SELECT _id FROM books)'
-			cursor.execute(query)
-			query = 'DELETE FROM collections WHERE collection_id NOT IN (SELECT _id FROM collection)'
-			cursor.execute(query)
-		
-			debug_print("Removing Orphaned Book Records")
-		
-			# Purge any references to books not in this database
-			# Idea is to prevent any spill-over where these wind up applying to some other book
-			query = 'DELETE FROM %s WHERE content_id NOT IN (SELECT _id FROM books)'
-			cursor.execute(query%'annotation')
-			cursor.execute(query%'bookmark')
-			cursor.execute(query%'current_position')
-			cursor.execute(query%'freehand')
-			cursor.execute(query%'history')
-			cursor.execute(query%'layout_cache')
-			cursor.execute(query%'preference')
-	
-			cursor.close()
-		except DatabaseError:
+            cursor = connection.cursor()
+        
+            debug_print("Removing Orphaned Collection Records")
+        
+            # Purge any collections references that point into the abyss
+            query = 'DELETE FROM collections WHERE content_id NOT IN (SELECT _id FROM books)'
+            cursor.execute(query)
+            query = 'DELETE FROM collections WHERE collection_id NOT IN (SELECT _id FROM collection)'
+            cursor.execute(query)
+        
+            debug_print("Removing Orphaned Book Records")
+        
+            # Purge any references to books not in this database
+            # Idea is to prevent any spill-over where these wind up applying to some other book
+            query = 'DELETE FROM %s WHERE content_id NOT IN (SELECT _id FROM books)'
+            cursor.execute(query%'annotation')
+            cursor.execute(query%'bookmark')
+            cursor.execute(query%'current_position')
+            cursor.execute(query%'freehand')
+            cursor.execute(query%'history')
+            cursor.execute(query%'layout_cache')
+            cursor.execute(query%'preference')
+    
+            cursor.close()
+        except DatabaseError:
             import traceback
             tb = traceback.format_exc()
             raise DeviceError((('The SONY database is corrupted. '