diff --git a/deepteam/vulnerabilities/custom/custom.py b/deepteam/vulnerabilities/custom/custom.py
index 24ddd4fc..2fdb4e82 100644
--- a/deepteam/vulnerabilities/custom/custom.py
+++ b/deepteam/vulnerabilities/custom/custom.py
@@ -41,6 +41,13 @@ def __init__(
             self.types = Enum(
                 f"CustomVulnerabilityType", {t.upper(): t for t in types}
             )
+        else:
+            # Default to a single type derived from the vulnerability name
+            # so iteration over self.types always works
+            self.types = Enum(
+                f"CustomVulnerabilityType",
+                {name.upper().replace(" ", "_"): name},
+            )
 
         self.custom_prompt = custom_prompt
         self.criteria = criteria.strip()
diff --git a/tests/test_core/test_vulnerabilities/test_custom_vulnerability.py b/tests/test_core/test_vulnerabilities/test_custom_vulnerability.py
index 5b0f7e3b..c4d7338f 100644
--- a/tests/test_core/test_vulnerabilities/test_custom_vulnerability.py
+++ b/tests/test_core/test_vulnerabilities/test_custom_vulnerability.py
@@ -19,3 +19,33 @@ def test_custom_vulnerability_initialize(self):
         assert sorted(
             type.value for type in custom_vulnerability.types
         ) == sorted(["type1", "type2"])
+
+    def test_custom_vulnerability_no_types(self):
+        """CustomVulnerability should not raise when types is omitted."""
+        custom_vulnerability = CustomVulnerability(
+            criteria="Criteria",
+            name="Data Leakage",
+        )
+        assert custom_vulnerability.name == "Data Leakage"
+        assert custom_vulnerability.criteria == "Criteria"
+        # Should have a default type derived from the name
+        type_values = [t.value for t in custom_vulnerability.types]
+        assert type_values == ["Data Leakage"]
+
+    def test_custom_vulnerability_no_types_get_name(self):
+        """get_name works when types is omitted."""
+        custom_vulnerability = CustomVulnerability(
+            criteria="Test criteria",
+            name="Test Vuln",
+        )
+        assert custom_vulnerability.get_name() == "Test Vuln"
+
+    def test_custom_vulnerability_single_type(self):
+        """CustomVulnerability works with a single type."""
+        custom_vulnerability = CustomVulnerability(
+            criteria="Criteria",
+            name="Name",
+            types=["only_type"],
+        )
+        type_values = [t.value for t in custom_vulnerability.types]
+        assert type_values == ["only_type"]