diff --git a/CHANGELOG.md b/CHANGELOG.md
index ab1afb9f..ebd95e96 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 # Changelog
 
 ## 3.7.7.dev
+* Fix: web plugin helpers httputils.serve_resource/serve_folder ignored their mimetypes and fallback_mimetype parameters and always used the built-in mapping, so custom web plugins could not serve additional file types with a correct Content-Type
 * Fix: free-busy REPORT always failed with HTTP 400 ("FREEBUSY occurrences limit of 0 hit") when [reporting] max_freebusy_occurrence is set to 0 (limit disabled), because the limit check did not honor the disabled limit
 * Fix: time-range filter treated a VEVENT with a whole-day DURATION (e.g. P1D, P2D) as zero-length (timedelta.seconds instead of total_seconds), so such events were missing from calendar-query REPORT results
 * Fix: calendar-data expand (REPORT) left recurrence properties (e.g. RDATE) on the expanded single-occurrence VEVENTs; a single try/except around the sequential delattr() calls stopped at the first absent property (e.g. missing EXDATE), so later ones were never removed
diff --git a/radicale/httputils.py b/radicale/httputils.py
index e030cdce..2259d5d7 100644
--- a/radicale/httputils.py
+++ b/radicale/httputils.py
@@ -209,8 +209,8 @@ def _serve_traversable(
         traversable = traversable.joinpath(index_file)
     if not traversable.is_file():
         return NOT_FOUND
-    content_type = MIMETYPES.get(
-        os.path.splitext(traversable.name)[1].lower(), FALLBACK_MIMETYPE)
+    content_type = mimetypes.get(
+        os.path.splitext(traversable.name)[1].lower(), fallback_mimetype)
     headers = {
         "Content-Type": content_type,
     }
diff --git a/radicale/tests/test_web.py b/radicale/tests/test_web.py
index ab4de538..f6e7964b 100644
--- a/radicale/tests/test_web.py
+++ b/radicale/tests/test_web.py
@@ -19,6 +19,7 @@ Test web plugin.
 
 """
 
+from radicale import httputils
 from radicale.tests import BaseTest
 
 
@@ -52,3 +53,20 @@ class TestBaseWebRequests(BaseTest):
         assert answer == "custom"
         _, answer = self.post("/.web", "body content")
         assert answer == "echo:body content"
+
+    def test_serve_resource_custom_mimetypes(self) -> None:
+        """serve_resource must honor mimetypes and fallback_mimetype."""
+        status, headers, _, _ = httputils.serve_resource(
+            "radicale.web", "internal_data", "", "/.web/index.html")
+        assert status == 200
+        assert dict(headers)["Content-Type"] == "text/html"
+        status, headers, _, _ = httputils.serve_resource(
+            "radicale.web", "internal_data", "", "/.web/index.html",
+            mimetypes={".html": "text/x-custom"})
+        assert status == 200
+        assert dict(headers)["Content-Type"] == "text/x-custom"
+        status, headers, _, _ = httputils.serve_resource(
+            "radicale.web", "internal_data", "", "/.web/index.html",
+            mimetypes={}, fallback_mimetype="application/x-fallback")
+        assert status == 200
+        assert dict(headers)["Content-Type"] == "application/x-fallback"