1 files changed, 9 insertions, 3 deletions
diff --git a/python/vyos/configdict.py b/python/vyos/configdict.py
index 53bd1a13e..785207c7f 100644
--- a/python/vyos/configdict.py
+++ b/python/vyos/configdict.py
@@ -309,12 +309,18 @@ def is_source_interface(conf, interface, intftype=None):
     """
     ret_val = None
     intftypes = ['macsec', 'pppoe', 'pseudo-ethernet', 'tunnel', 'vxlan']
-    if intftype not in intftypes + [None]:
+    if not intftype:
+        intftype = intftypes
+
+    if isinstance(intftype, str):
+        intftype = [intftype]
+    elif not isinstance(intftype, list):
+        raise ValueError(f'Interface type "{type(intftype)}" must be either str or list!')
+
+    if not all(x in intftypes for x in intftype):
         raise ValueError(f'unknown interface type "{intftype}" or it can not '
             'have a source-interface')
 
-    intftype = intftypes if intftype == None else [intftype]
-
     # set config level to root
     old_level = conf.get_level()
     conf.set_level([])