diff --git a/oml/item/scan.py b/oml/item/scan.py
index 72e2dd9..390ad81 100644
--- a/oml/item/scan.py
+++ b/oml/item/scan.py
@@ -30,8 +30,7 @@ def remove_missing(books=None):
     if books is None:
         books = collect_books()
     with db.session():
-        prefs = settings.preferences
-        prefix = os.path.join(os.path.expanduser(prefs['libraryPath']), 'Books' + os.sep)
+        prefix = get_prefix()
         if os.path.exists(prefix):
             logger.debug('scan for removed files')
             db_paths = []
@@ -90,14 +89,18 @@ def add_file(id, f, prefix, from_=None, commit=True):
     logger.debug('%s added', id)
     return file
 
-def collect_books():
+def get_prefix():
     prefs = settings.preferences
     prefix = os.path.join(os.path.expanduser(prefs['libraryPath']), 'Books' + os.sep)
     if not prefix[-1] == os.sep:
         prefix += os.sep
     assert isinstance(prefix, str)
+    return prefix
+
+def collect_books():
     logger.debug('collect books')
     books = []
+    prefix = get_prefix()
     for root, folders, files in os.walk(prefix):
         for f in files:
             if state.shutdown:
@@ -115,6 +118,7 @@ def collect_books():
 
 def run_scan():
     logger.debug('run_scan')
+    prefix = get_prefix()
     books = collect_books()
     remove_missing(books)
 
@@ -159,7 +163,7 @@ def run_import(options=None):
         prefix = os.path.realpath(prefix)
     if not prefix[-1] == os.sep:
         prefix += os.sep
-    prefix_books = os.path.join(os.path.expanduser(prefs['libraryPath']), 'Books' + os.sep)
+    prefix_books = get_prefix()
     prefix_imported = os.path.join(prefix_books, '.import' + os.sep)
     if prefix_books.startswith(prefix) or prefix.startswith(prefix_books):
         error = 'invalid path'