diff --git a/radicale/app/__init__.py b/radicale/app/__init__.py
index fdf0d1f..685fb77 100644
--- a/radicale/app/__init__.py
+++ b/radicale/app/__init__.py
@@ -191,6 +191,12 @@ class Application(ApplicationPartDelete, ApplicationPartHead,
         base_prefix_src = ("HTTP_X_SCRIPT_NAME" if "HTTP_X_SCRIPT_NAME" in
                            environ else "SCRIPT_NAME")
         base_prefix = environ.get(base_prefix_src, "")
+        if base_prefix.endswith("/"):
+            logger.error("Base prefix (from %s) must not end with '/': %r",
+                         base_prefix_src, base_prefix)
+            if base_prefix_src == "HTTP_X_SCRIPT_NAME":
+                return response(*httputils.BAD_REQUEST)
+            return response(*httputils.INTERNAL_SERVER_ERROR)
         logger.debug("Base prefix (from %s): %r", base_prefix_src, base_prefix)
         # Sanitize request URI (a WSGI server indicates with an empty path,
         # that the URL targets the application root without a trailing slash)
diff --git a/radicale/tests/test_base.py b/radicale/tests/test_base.py
index 8c89cf4..ea01cf6 100644
--- a/radicale/tests/test_base.py
+++ b/radicale/tests/test_base.py
@@ -65,6 +65,10 @@ permissions: RrWw""")
                                          SCRIPT_NAME="/radicale")
             assert headers.get("Location") == "/radicale/.web"
 
+    def test_root_broken_script_name(self) -> None:
+        """GET request at "/" with SCRIPT_NAME ending with "/"."""
+        self.get("/", check=500, SCRIPT_NAME="/radicale/")
+
     def test_root_http_x_script_name(self) -> None:
         """GET request at "/" with HTTP_X_SCRIPT_NAME."""
         for path in ["", "/", "//"]:
@@ -72,6 +76,10 @@ permissions: RrWw""")
                                          HTTP_X_SCRIPT_NAME="/radicale")
             assert headers.get("Location") == "/radicale/.web"
 
+    def test_root_broken_http_x_script_name(self) -> None:
+        """GET request at "/" with HTTP_X_SCRIPT_NAME ending with "/"."""
+        self.get("/", check=400, HTTP_X_SCRIPT_NAME="/radicale/")
+
     def test_sanitized_path(self) -> None:
         """GET request with unsanitized paths."""
         for path, sane_path in [