diff --git a/openstack/block_storage/v3/_proxy.py b/openstack/block_storage/v3/_proxy.py
index b7cfef0c6..421644aa0 100644
--- a/openstack/block_storage/v3/_proxy.py
+++ b/openstack/block_storage/v3/_proxy.py
@@ -2024,7 +2024,9 @@ class Proxy(proxy.Proxy):
         res = self._get_resource(
             _quota_set.QuotaSet, None, project_id=project.id
         )
-        return res.fetch(self, base_path='/os-quota-sets/defaults')
+        return res.fetch(
+            self, base_path=(f'/os-quota-sets/{project.id}/defaults')
+        )
 
     def revert_quota_set(self, project, **query):
         """Reset Quota for the project/user.
diff --git a/openstack/tests/unit/block_storage/v3/test_proxy.py b/openstack/tests/unit/block_storage/v3/test_proxy.py
index 67f8778a7..eb4cbfe8e 100644
--- a/openstack/tests/unit/block_storage/v3/test_proxy.py
+++ b/openstack/tests/unit/block_storage/v3/test_proxy.py
@@ -1176,14 +1176,15 @@ class TestQuotaSet(TestVolumeProxy):
         )
 
     def test_quota_set_get_defaults(self):
+        project_id = 'prj'
         self._verify(
             'openstack.resource.Resource.fetch',
             self.proxy.get_quota_set_defaults,
-            method_args=['prj'],
+            method_args=[project_id],
             expected_args=[
                 self.proxy,
                 False,
-                '/os-quota-sets/defaults',
+                f'/os-quota-sets/{project_id}/defaults',
                 None,
                 False,
             ],
diff --git a/releasenotes/notes/fix-quota-show-defaults-0a8c388926eae18b.yaml b/releasenotes/notes/fix-quota-show-defaults-0a8c388926eae18b.yaml
new file mode 100644
index 000000000..428abef0e
--- /dev/null
+++ b/releasenotes/notes/fix-quota-show-defaults-0a8c388926eae18b.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed issue with ``quota show --default`` command by
+    correcting the API URL.