diff --git a/config/main.py b/config/main.py
index 0f2d9296f4..46cec34e43 100644
--- a/config/main.py
+++ b/config/main.py
@@ -1032,6 +1032,8 @@ def validate_ipv4_address(ctx, param, ip_addr):
 def validate_gre_type(ctx, _, value):
     """A validator for validating input gre_type
     """
+    if value is None:
+        return None
     try:
         base = 10
         if value.lower().startswith('0x'):
diff --git a/tests/config_mirror_session_test.py b/tests/config_mirror_session_test.py
index 986df2e711..a26e109a6d 100644
--- a/tests/config_mirror_session_test.py
+++ b/tests/config_mirror_session_test.py
@@ -80,6 +80,18 @@ def test_mirror_session_add():
 
         mocked.assert_called_with("test_session", "100.1.1.1", "2.2.2.2", 8, 63, 0x1234, 100, None)
 
+        result = runner.invoke(
+                config.config.commands["mirror_session"].commands["add"],
+                ["test_session", "100.1.1.1", "2.2.2.2", "8", "63", "0", "0"])
+
+        mocked.assert_called_with("test_session", "100.1.1.1", "2.2.2.2", 8, 63, 0, 0, None)
+        
+        result = runner.invoke(
+                config.config.commands["mirror_session"].commands["add"],
+                ["test_session", "100.1.1.1", "2.2.2.2", "8", "63"])
+
+        mocked.assert_called_with("test_session", "100.1.1.1", "2.2.2.2", 8, 63, None, None, None)
+
 
 def test_mirror_session_erspan_add():
     runner = CliRunner()