2 files changed, 3 insertions, 3 deletions
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index c97e0df1f5..bfd46a3730 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -86,8 +86,8 @@ REQUIREMENTS = [
 
 CONDITIONAL_REQUIREMENTS = {
     "matrix-synapse-ldap3": ["matrix-synapse-ldap3>=0.1"],
-    # we use execute_batch, which arrived in psycopg 2.7.
-    "postgres": ["psycopg2>=2.7"],
+    # we use execute_values with the fetch param, which arrived in psycopg 2.8.
+    "postgres": ["psycopg2>=2.8"],
     # ACME support is required to provision TLS certificates from authorities
     # that use the protocol, such as Let's Encrypt.
     "acme": [
diff --git a/synapse/util/iterutils.py b/synapse/util/iterutils.py
index 6ef2b008a4..8d2411513f 100644
--- a/synapse/util/iterutils.py
+++ b/synapse/util/iterutils.py
@@ -78,7 +78,7 @@ def sorted_topologically(
         if node not in degree_map:
             continue
 
-        for edge in edges:
+        for edge in set(edges):
             if edge in degree_map:
                 degree_map[node] += 1