Index: django/db/backends/sqlite3/creation.py
===================================================================
--- django/db/backends/sqlite3/creation.py	(revision 17581)
+++ django/db/backends/sqlite3/creation.py	(working copy)
@@ -72,3 +72,16 @@
 
     def set_autocommit(self):
         self.connection.connection.isolation_level = None
+
+    def test_db_signature(self):
+        """
+        Returns a tuple that uniquely identifies a database.
+
+        This takes into account the special cases of ":memory:" and "" for
+        SQLite since the databases will be distinct despite having the same
+        NAME. See http://www.sqlite.org/inmemorydb.html
+        """
+        sig = (self.connection.settings_dict['NAME'],)
+        if name in [':memory:', '']:
+            sig += (id(self.connection),)
+        return sig