diff --git a/src/pretix/base/middleware.py b/src/pretix/base/middleware.py
index 253f335a3..0401a1477 100644
--- a/src/pretix/base/middleware.py
+++ b/src/pretix/base/middleware.py
@@ -3,7 +3,8 @@ from urllib.parse import urlsplit
 
 import pytz
 from django.conf import settings
-from django.http import HttpRequest, HttpResponse
+from django.http import HttpRequest, HttpResponse, Http404
+from django.middleware.common import CommonMiddleware
 from django.urls import get_script_prefix
 from django.utils import timezone, translation
 from django.utils.cache import patch_vary_headers
@@ -252,3 +253,15 @@ class SecurityMiddleware(MiddlewareMixin):
             del resp['Content-Security-Policy']
 
         return resp
+
+
+class CustomCommonMiddleware(CommonMiddleware):
+
+    def get_full_path_with_slash(self, request):
+        """
+        Raise an error regardless of DEBUG mode when in POST, PUT, or PATCH.
+        """
+        new_path = super().get_full_path_with_slash(request)
+        if request.method in ('POST', 'PUT', 'PATCH'):
+            raise Http404('Please append a / at the end of the URL')
+        return new_path
diff --git a/src/pretix/settings.py b/src/pretix/settings.py
index dea8de0a5..69a3d5c2e 100644
--- a/src/pretix/settings.py
+++ b/src/pretix/settings.py
@@ -351,7 +351,7 @@ CORE_MODULES = {
 MIDDLEWARE = [
     'pretix.api.middleware.IdempotencyMiddleware',
     'pretix.multidomain.middlewares.MultiDomainMiddleware',
-    'django.middleware.common.CommonMiddleware',
+    'pretix.base.middleware.CustomCommonMiddleware',
     'pretix.multidomain.middlewares.SessionMiddleware',
     'pretix.multidomain.middlewares.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
@@ -375,7 +375,7 @@ except ImportError:
 
 
 if METRICS_ENABLED:
-    MIDDLEWARE.insert(MIDDLEWARE.index('django.middleware.common.CommonMiddleware') + 1,
+    MIDDLEWARE.insert(MIDDLEWARE.index('pretix.base.middleware.CustomCommonMiddleware') + 1,
                       'pretix.helpers.metrics.middleware.MetricsMiddleware')