diff --git a/ironic/common/pxe_utils.py b/ironic/common/pxe_utils.py
index ad34f43056..ecc573504c 100644
--- a/ironic/common/pxe_utils.py
+++ b/ironic/common/pxe_utils.py
@@ -925,8 +925,9 @@ def prepare_instance_pxe_config(task, image_info,
 @image_cache.cleanup(priority=25)
 class TFTPImageCache(image_cache.ImageCache):
     def __init__(self):
+        master_path = CONF.pxe.tftp_master_path or None
         super(TFTPImageCache, self).__init__(
-            CONF.pxe.tftp_master_path,
+            master_path,
             # MiB -> B
             cache_size=CONF.pxe.image_cache_size * 1024 * 1024,
             # min -> sec
diff --git a/ironic/conf/pxe.py b/ironic/conf/pxe.py
index f16aa94e04..49882ebfe6 100644
--- a/ironic/conf/pxe.py
+++ b/ironic/conf/pxe.py
@@ -76,7 +76,7 @@ opts = [
                default='/tftpboot/master_images',
                help=_('On ironic-conductor node, directory where master TFTP '
                       'images are stored on disk. '
-                      'Setting to <None> disables image caching.')),
+                      'Setting to the empty string disables image caching.')),
     cfg.IntOpt('dir_permission',
                help=_("The permission that will be applied to the TFTP "
                       "folders upon creation. This should be set to the "
diff --git a/ironic/tests/unit/common/test_pxe_utils.py b/ironic/tests/unit/common/test_pxe_utils.py
index 5d99f06105..87f64c2630 100644
--- a/ironic/tests/unit/common/test_pxe_utils.py
+++ b/ironic/tests/unit/common/test_pxe_utils.py
@@ -1740,3 +1740,29 @@ class CleanUpPxeEnvTestCase(db_base.DbTestCase):
             mock_pxe_clean.assert_called_once_with(task, ipxe_enabled=False)
             mock_unlink.assert_any_call('deploy_kernel')
         mock_cache.return_value.clean_up.assert_called_once_with()
+
+
+class TFTPImageCacheTestCase(db_base.DbTestCase):
+    @mock.patch.object(fileutils, 'ensure_tree')
+    def test_with_master_path(self, mock_ensure_tree):
+        self.config(tftp_master_path='/fake/path', group='pxe')
+        self.config(image_cache_size=500, group='pxe')
+        self.config(image_cache_ttl=30, group='pxe')
+
+        cache = pxe_utils.TFTPImageCache()
+
+        mock_ensure_tree.assert_called_once_with('/fake/path')
+        self.assertEqual(500 * 1024 * 1024, cache._cache_size)
+        self.assertEqual(30 * 60, cache._cache_ttl)
+
+    @mock.patch.object(fileutils, 'ensure_tree')
+    def test_without_master_path(self, mock_ensure_tree):
+        self.config(tftp_master_path='', group='pxe')
+        self.config(image_cache_size=500, group='pxe')
+        self.config(image_cache_ttl=30, group='pxe')
+
+        cache = pxe_utils.TFTPImageCache()
+
+        mock_ensure_tree.assert_not_called()
+        self.assertEqual(500 * 1024 * 1024, cache._cache_size)
+        self.assertEqual(30 * 60, cache._cache_ttl)
diff --git a/releasenotes/notes/fix-tftp-master-path-config-77face94f5db9af7.yaml b/releasenotes/notes/fix-tftp-master-path-config-77face94f5db9af7.yaml
new file mode 100644
index 0000000000..0769ceddcf
--- /dev/null
+++ b/releasenotes/notes/fix-tftp-master-path-config-77face94f5db9af7.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixes an issue where the master TFTP image cache could not be disbled.
+    The configuration option ``[pxe]/tftp_master_path`` may now be set to
+    the empty string to disable the cache. For more information, see
+    story `2004608 <https://storyboard.openstack.org/#!/story/2004608>`_.