diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
index e63a9716bb9..e7fd5a5522a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
@@ -517,18 +517,20 @@ public class DefaultGenerator implements Generator {
                 }
 
                 // TODO revise below as we've already performed unaliasing so that the isAlias check may be removed
-                Map<String, Object> modelTemplate = (Map<String, Object>) ((List<Object>) models.get("models")).get(0);
-                if (modelTemplate != null && modelTemplate.containsKey("model")) {
-                    CodegenModel m = (CodegenModel) modelTemplate.get("model");
-                    if (m.isAlias && !(config instanceof PythonClientCodegen))  {
-                        // alias to number, string, enum, etc, which should not be generated as model
-                        // for PythonClientCodegen, all aliases are generated as models
-                        continue;  // Don't create user-defined classes for aliases
+                List<Object> modelList = (List<Object>) models.get("models");
+                if (modelList != null && !modelList.isEmpty()) {
+                    Map<String, Object> modelTemplate = (Map<String, Object>) modelList.get(0);
+                    if (modelTemplate != null && modelTemplate.containsKey("model")) {
+                        CodegenModel m = (CodegenModel) modelTemplate.get("model");
+                        if (m.isAlias && !(config instanceof PythonClientCodegen))  {
+                            // alias to number, string, enum, etc, which should not be generated as model
+                            // for PythonClientCodegen, all aliases are generated as models
+                            continue;  // Don't create user-defined classes for aliases
+                        }
                     }
+                    allModels.add(modelTemplate);
                 }
 
-                allModels.add(modelTemplate);
-
                 // to generate model files
                 generateModel(files, models, modelName);