diff --git a/synapse/docker-compose.py35.pg95.yaml b/synapse/docker-compose.py35.pg95.yaml
index 027c825..c6e8280 100644
--- a/synapse/docker-compose.py35.pg95.yaml
+++ b/synapse/docker-compose.py35.pg95.yaml
@@ -6,6 +6,7 @@ services:
     image: postgres:9.5
     environment:
       POSTGRES_PASSWORD: postgres
+      POSTGRES_INITDB_ARGS: "--lc-collate C --lc-ctype C --encoding UTF8"
     command: -c fsync=off
 
   testenv:
diff --git a/synapse/docker-compose.py37.pg11.yaml b/synapse/docker-compose.py37.pg11.yaml
index 242c467..411c37f 100644
--- a/synapse/docker-compose.py37.pg11.yaml
+++ b/synapse/docker-compose.py37.pg11.yaml
@@ -6,6 +6,7 @@ services:
     image: postgres:11
     environment:
       POSTGRES_PASSWORD: postgres
+      POSTGRES_INITDB_ARGS: "--lc-collate C --lc-ctype C --encoding UTF8"
     command: -c fsync=off
 
   testenv:
diff --git a/synapse/docker-compose.py37.pg95.yaml b/synapse/docker-compose.py37.pg95.yaml
index c87a63d..54ca794 100644
--- a/synapse/docker-compose.py37.pg95.yaml
+++ b/synapse/docker-compose.py37.pg95.yaml
@@ -6,6 +6,7 @@ services:
     image: postgres:9.5
     environment:
       POSTGRES_PASSWORD: postgres
+      POSTGRES_INITDB_ARGS: "--lc-collate C --lc-ctype C --encoding UTF8"
     command: -c fsync=off
 
   testenv:
diff --git a/synapse/docker-compose.py38.pg12.yaml b/synapse/docker-compose.py38.pg12.yaml
index 8320a1b..934a34c 100644
--- a/synapse/docker-compose.py38.pg12.yaml
+++ b/synapse/docker-compose.py38.pg12.yaml
@@ -6,6 +6,7 @@ services:
     image: postgres:12
     environment:
       POSTGRES_PASSWORD: postgres
+      POSTGRES_INITDB_ARGS: "--lc-collate C --lc-ctype C --encoding UTF8"
     command: -c fsync=off
 
   testenv: