diff --git a/api/conf/settings/base.py b/api/conf/settings/base.py
index d3203f94a78..c49dcc3a0f8 100644
--- a/api/conf/settings/base.py
+++ b/api/conf/settings/base.py
@@ -6,7 +6,6 @@
     "django.contrib.messages",
     "django.contrib.staticfiles",
     # Third-party installed apps, more can be added in other settings files.
-    "corsheaders",
     "sslserver",
 ]
 
diff --git a/api/conf/settings/logging.py b/api/conf/settings/logging.py
index de60a8ca82a..495827bd760 100644
--- a/api/conf/settings/logging.py
+++ b/api/conf/settings/logging.py
@@ -115,6 +115,8 @@ def health_check_filter(record: LogRecord) -> bool:
 
     if not DEBUG:
         # WARNING: Do not run in production long-term as it can impact performance.
-        MIDDLEWARE.append(
-            "api.middleware.force_debug_cursor_middleware.force_debug_cursor_middleware"  # noqa: E501
+        middleware = (
+            "api.middleware.force_debug_cursor_middleware.force_debug_cursor_middleware"
         )
+        if middleware not in MIDDLEWARE:
+            MIDDLEWARE.append(middleware)
diff --git a/api/conf/settings/oauth2.py b/api/conf/settings/oauth2.py
index ca09cc3990a..37d851401ee 100644
--- a/api/conf/settings/oauth2.py
+++ b/api/conf/settings/oauth2.py
@@ -3,13 +3,12 @@
 from conf.settings.base import INSTALLED_APPS, MIDDLEWARE
 
 
-INSTALLED_APPS += [
-    "oauth2_provider",
-]
+if "oauth2_provider" not in INSTALLED_APPS:
+    INSTALLED_APPS.append("oauth2_provider")
 
-MIDDLEWARE += [
-    "oauth2_provider.middleware.OAuth2TokenMiddleware",
-]
+middleware = "oauth2_provider.middleware.OAuth2TokenMiddleware"
+if middleware not in MIDDLEWARE:
+    MIDDLEWARE.append(middleware)
 
 OAUTH2_PROVIDER = {
     "SCOPES": {
diff --git a/api/conf/settings/openverse.py b/api/conf/settings/openverse.py
index 02631153810..ff716941d4b 100644
--- a/api/conf/settings/openverse.py
+++ b/api/conf/settings/openverse.py
@@ -1,6 +1,5 @@
 from conf.settings.base import INSTALLED_APPS
 
 
-INSTALLED_APPS += [
-    "api",
-]
+if "api" not in INSTALLED_APPS:
+    INSTALLED_APPS.append("api")
diff --git a/api/conf/settings/rest_framework.py b/api/conf/settings/rest_framework.py
index 1ced0971b05..b994d45c197 100644
--- a/api/conf/settings/rest_framework.py
+++ b/api/conf/settings/rest_framework.py
@@ -3,9 +3,8 @@
 from conf.settings.base import INSTALLED_APPS
 
 
-INSTALLED_APPS += [
-    "rest_framework",
-]
+if "rest_framework" not in INSTALLED_APPS:
+    INSTALLED_APPS.append("rest_framework")
 
 
 THROTTLE_ANON_BURST = config("THROTTLE_ANON_BURST", default="5/hour")
diff --git a/api/conf/settings/s3.py b/api/conf/settings/s3.py
index c21078c86b0..bcbef2b3c6f 100644
--- a/api/conf/settings/s3.py
+++ b/api/conf/settings/s3.py
@@ -10,9 +10,8 @@
 
 
 if USE_S3:
-    INSTALLED_APPS += [
-        "storages",
-    ]
+    if "storages" not in INSTALLED_APPS:
+        INSTALLED_APPS.append("storages")
 
     STORAGES["default"]["BACKEND"] = "storages.backends.s3boto3.S3Boto3Storage"
 
diff --git a/api/conf/settings/security.py b/api/conf/settings/security.py
index af5bdef5490..22182999788 100644
--- a/api/conf/settings/security.py
+++ b/api/conf/settings/security.py
@@ -2,6 +2,8 @@
 
 from decouple import config
 
+from conf.settings.base import INSTALLED_APPS, MIDDLEWARE
+
 
 # Quick-start development settings - unsuitable for production
 # See https://docs.djangoproject.com/en/4.2/howto/deployment/checklist/
@@ -35,6 +37,13 @@
 CSRF_TRUSTED_ORIGINS = ["https://*.openverse.engineering"]
 
 # Allow anybody to access the API from any domain
+if "corsheaders" not in INSTALLED_APPS:
+    INSTALLED_APPS.append("corsheaders")
+
+middleware = "corsheaders.middleware.CorsMiddleware"
+if middleware not in MIDDLEWARE:
+    MIDDLEWARE.insert(0, middleware)
+
 CORS_ORIGIN_ALLOW_ALL = True
 
 # Proxy handling, for production
diff --git a/api/conf/settings/spectacular.py b/api/conf/settings/spectacular.py
index 690750350d7..e1165db07de 100644
--- a/api/conf/settings/spectacular.py
+++ b/api/conf/settings/spectacular.py
@@ -4,9 +4,8 @@
 from conf.settings.misc import API_VERSION
 
 
-INSTALLED_APPS += [
-    "drf_spectacular",
-]
+if "drf_spectacular" not in INSTALLED_APPS:
+    INSTALLED_APPS.append("drf_spectacular")
 
 SPECTACULAR_SETTINGS = {
     "TITLE": "Openverse API",