diff --git a/db_structure.xml b/db_structure.xml
index 82d2a731d4..2df218d359 100644
--- a/db_structure.xml
+++ b/db_structure.xml
@@ -67,8 +67,7 @@
    <field>
 	   <name>path_hash</name>
 	   <type>text</type>
-	   <default>
-	   </default>
+	   <default></default>
 	   <notnull>true</notnull>
 	   <length>32</length>
    </field>
diff --git a/files/ajax/scan.php b/files/ajax/scan.php
index 565275911b..db09b7d5c6 100644
--- a/files/ajax/scan.php
+++ b/files/ajax/scan.php
@@ -17,6 +17,7 @@ if($force or !OC_FileCache::inCache('')){
 	if(!$checkOnly){
 		OC_DB::beginTransaction();
 		OC_FileCache::scan('',$eventSource);
+		OC_FileCache::clean();
 		OC_DB::commit();
 		$eventSource->send('success',true);
 	}else{
diff --git a/lib/filecache.php b/lib/filecache.php
index a8c48e3f14..86d865ed9f 100644
--- a/lib/filecache.php
+++ b/lib/filecache.php
@@ -637,6 +637,14 @@ class OC_FileCache{
 			self::fileSystemWatcherWrite(array('path'=>$path),$root);
 		}
 	}
+
+	/**
+	 * clean old pre-path_hash entries
+	 */
+	public static function clean(){
+		$query=OC_DB::prepare('DELETE FROM *PREFIX*fscache WHERE LENGTH(path_hash)<30');
+		$query->execute();
+	}
 }
 
 //watch for changes and try to keep the cache up to date