1 files changed, 20 insertions, 10 deletions
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index e404fa72de..a6aa64f9fb 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -458,17 +458,27 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
 
     @defer.inlineCallbacks
     def get_user_id_by_threepid(self, medium, address):
-        ret = yield self._simple_select_one(
-            "user_threepids",
-            {
-                "medium": medium,
-                "address": address
-            },
-            ['user_id'], True, 'get_user_id_by_threepid'
+        def f(txn):
+            sql = (
+                "SELECT user_id"
+                " FROM user_threepids"
+                " WHERE medium = ? AND LOWER(address) = LOWER(?)"
+            )
+            txn.execute(sql, (medium, address))
+            row = txn.fetchone()
+            if not row:
+                return None
+            if txn.rowcount > 1:
+                raise StoreError(500, "More than one row matched")
+            return {
+                "user_id": row[0]
+            }
+
+        res = yield self.runInteraction(
+            "get_user_id_by_threepid", f
         )
-        if ret:
-            defer.returnValue(ret['user_id'])
-        defer.returnValue(None)
+
+        defer.returnValue(res)
 
     def user_delete_threepids(self, user_id):
         return self._simple_delete(