diff --git a/openapi2jsonschema/command.py b/openapi2jsonschema/command.py
index 9cd1bfc..1fd7083 100644
--- a/openapi2jsonschema/command.py
+++ b/openapi2jsonschema/command.py
@@ -94,6 +94,10 @@ def default(output, schema, prefix, stand_alone, expanded, kubernetes, strict):
                 # For Kubernetes, populate `apiVersion` and `kind` properties from `x-kubernetes-group-version-kind`
                 for type_name in definitions:
                     type_def = definitions[type_name]
+                    if "properties" not in type_def:
+                        error(f"{type_name} has no properties")
+                        continue
+
                     if "x-kubernetes-group-version-kind" in type_def:
                         for kube_ext in type_def["x-kubernetes-group-version-kind"]:
                             if expanded and "apiVersion" in type_def["properties"]: