diff --git a/neutron/db/quota/driver.py b/neutron/db/quota/driver.py
index 694a40735fa..fc6dffc52c4 100644
--- a/neutron/db/quota/driver.py
+++ b/neutron/db/quota/driver.py
@@ -97,7 +97,12 @@ def get_detailed_project_quotas(self, context, resources, project_id):
                 # pass it regardless to keep the quota driver API intact
                 plugins = directory.get_plugins()
                 plugin = plugins.get(key, plugins[constants.CORE])
-                used = resource.count(context, plugin, project_id)
+                try:
+                    used = resource.count(context, plugin, project_id)
+                except NotImplementedError:
+                    LOG.info('Skipping quota resource %s: no plugin loaded '
+                             'that supports counting it.', key)
+                    continue
 
             project_quota_ext[key] = {
                 'limit': resource.default,
@@ -108,7 +113,8 @@ def get_detailed_project_quotas(self, context, resources, project_id):
         quota_objs = quota_obj.Quota.get_objects(context,
                                                  project_id=project_id)
         for item in quota_objs:
-            project_quota_ext[item['resource']]['limit'] = item['limit']
+            if item['resource'] in project_quota_ext:
+                project_quota_ext[item['resource']]['limit'] = item['limit']
         return project_quota_ext
 
     @staticmethod
diff --git a/neutron/tests/unit/db/quota/test_driver.py b/neutron/tests/unit/db/quota/test_driver.py
index d3f0f7c3cc7..362279efb23 100644
--- a/neutron/tests/unit/db/quota/test_driver.py
+++ b/neutron/tests/unit/db/quota/test_driver.py
@@ -308,6 +308,28 @@ def test_get_detailed_project_quotas_multiple_resource(self):
         self.assertEqual(7, detailed_quota[self.resource_2]['reserved'])
         self.assertEqual(3, detailed_quota[self.resource_2]['used'])
 
+    def test_get_detailed_project_quotas_skips_uncount_resource(self):
+        def _raise_not_implemented(context, resource, project_id):
+            raise NotImplementedError(
+                'No plugins that support counting %s found.' % resource)
+
+        resources = {
+            self.resource_1:
+                TestTrackedResource(self.resource_1, test_quota.MehModel),
+            self.resource_2:
+                TestCountableResource(self.resource_2,
+                                      _raise_not_implemented)}
+        self.plugin.update_quota_limit(self.context, self.project_1,
+                                       self.resource_1, 6)
+        self.plugin.update_quota_limit(self.context, self.project_1,
+                                       self.resource_2, 9)
+        detailed_quota = self.plugin.get_detailed_project_quotas(
+            self.context, resources, self.project_1)
+
+        self.assertIn(self.resource_1, detailed_quota)
+        self.assertNotIn(self.resource_2, detailed_quota)
+        self.assertEqual(6, detailed_quota[self.resource_1]['limit'])
+
     def test_quota_limit_check(self):
         resources = self._create_resources()
         self.plugin.update_quota_limit(self.context, self.project_1,
diff --git a/releasenotes/notes/fix-quota-details-unloaded-service-plugin-f4c2a0766eb045b0.yaml b/releasenotes/notes/fix-quota-details-unloaded-service-plugin-f4c2a0766eb045b0.yaml
new file mode 100644
index 00000000000..636cd66722d
--- /dev/null
+++ b/releasenotes/notes/fix-quota-details-unloaded-service-plugin-f4c2a0766eb045b0.yaml
@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixed a 500 Internal Server Error when querying the quota details API
+    (``GET /v2.0/quotas/{project_id}/details``) while a service plugin
+    package (e.g. ``neutron-fwaas``, ``neutron-vpnaas``,
+    ``networking-sfc``) is installed but its service plugin is not
+    configured in ``service_plugins``. The quota engine now gracefully
+    skips resources whose service plugin is not loaded instead of raising
+    a ``NotImplementedError``.