diff --git a/pubs/filebroker.py b/pubs/filebroker.py
index c6b1b0d..012c062 100644
--- a/pubs/filebroker.py
+++ b/pubs/filebroker.py
@@ -71,12 +71,12 @@ class FileBroker(object):
             os.remove(bibfilepath)
 
     def exists(self, citekey, both=True):
+        meta_exists = check_file(os.path.join(self.metadir, citekey + '.yaml'), fail=False)
+        bib_exists = check_file(os.path.join(self.bibdir, citekey + '.bib'), fail=False)
         if both:
-            return (check_file(os.path.join(self.metadir, citekey + '.yaml'), fail=False) and
-                    check_file(os.path.join(self.bibdir, citekey + '.bib'), fail=False))
+            return meta_exists and bib_exists
         else:
-            return (check_file(os.path.join(self.metadir, citekey + '.yaml'), fail=False) or
-                    check_file(os.path.join(self.bibdir, citekey + '.bib'), fail=False))
+            return meta_exists or bib_exists
 
 
     def listing(self, filestats=True):
diff --git a/pubs/repo.py b/pubs/repo.py
index e5c68fa..bdaf43d 100644
--- a/pubs/repo.py
+++ b/pubs/repo.py
@@ -1,5 +1,3 @@
-import shutil
-import glob
 import itertools
 
 from . import bibstruct
@@ -7,6 +5,7 @@ from . import events
 from . import datacache
 from .paper import Paper
 
+
 def _base27(n):
     return _base27((n - 1) // 26) + chr(ord('a') + ((n - 1) % 26)) if n else ''
 
@@ -65,9 +64,8 @@ class Repository(object):
                                if True, mimick the behavior of updating a paper
         """
         bibstruct.check_citekey(paper.citekey)
-        if (not overwrite) and self.databroker.exists(paper.citekey, both = False):
-            raise IOError('files using the {} citekey already exists'.format(paper.citekey))
-        if (not overwrite) and self.citekeys is not None and paper.citekey in self.citekeys:
+        if (not overwrite) and (self.databroker.exists(paper.citekey, both=False)
+                                or (citekey in self)):
             raise CiteKeyCollision('citekey {} already in use'.format(paper.citekey))
 
         self.databroker.push_bibdata(paper.citekey, paper.bibdata)
@@ -138,4 +136,3 @@ class Repository(object):
         for p in self.all_papers():
             tags = tags.union(p.tags)
         return tags
-