diff --git a/vdirsyncer/exceptions.py b/vdirsyncer/exceptions.py
index a5e541b..8acf654 100644
--- a/vdirsyncer/exceptions.py
+++ b/vdirsyncer/exceptions.py
@@ -42,7 +42,8 @@ class NotFoundError(PreconditionFailed):
 
 
 class AlreadyExistingError(PreconditionFailed):
-    '''Item already exists'''
+    '''Item already exists.'''
+    existing_href = None
 
 
 class WrongEtagError(PreconditionFailed):
diff --git a/vdirsyncer/storage/filesystem.py b/vdirsyncer/storage/filesystem.py
index 5d8e03d..68658f0 100644
--- a/vdirsyncer/storage/filesystem.py
+++ b/vdirsyncer/storage/filesystem.py
@@ -138,7 +138,7 @@ class FilesystemStorage(Storage):
                 return fpath, get_etag_from_fileobject(f)
         except OSError as e:
             if e.errno == errno.EEXIST:
-                raise exceptions.AlreadyExistingError(item)
+                raise exceptions.AlreadyExistingError(existing_href=href)
             else:
                 raise
 
diff --git a/vdirsyncer/storage/memory.py b/vdirsyncer/storage/memory.py
index 8a32f3d..765f8cd 100644
--- a/vdirsyncer/storage/memory.py
+++ b/vdirsyncer/storage/memory.py
@@ -41,7 +41,7 @@ class MemoryStorage(Storage):
     def upload(self, item):
         href = self._get_href(item)
         if href in self.items:
-            raise exceptions.AlreadyExistingError(item)
+            raise exceptions.AlreadyExistingError(existing_href=href)
         etag = _random_string()
         self.items[href] = (etag, item)
         return href, etag
diff --git a/vdirsyncer/storage/singlefile.py b/vdirsyncer/storage/singlefile.py
index 45ca28f..8232c93 100644
--- a/vdirsyncer/storage/singlefile.py
+++ b/vdirsyncer/storage/singlefile.py
@@ -134,7 +134,7 @@ class SingleFileStorage(Storage):
     def upload(self, item):
         href = item.ident
         if href in self._items:
-            raise exceptions.AlreadyExistingError(href)
+            raise exceptions.AlreadyExistingError(existing_href=href)
 
         self._items[href] = item, item.hash
         return href, item.hash