diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 60c91bf9c446..dcdad60d1816 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -675,7 +675,6 @@ private boolean codegenPropertyIsNew(CodegenModel model, CodegenProperty propert
      */
     protected Map<String, Schema> getModelNameToSchemaCache() {
         if (modelNameToSchemaCache == null) {
-            // Create a cache to efficiently lookup schema based on model name.
             Map<String, Schema> m = new HashMap<>();
             ModelUtils.getSchemas(openAPI).forEach((key, schema) -> m.put(toModelName(key), schema));
             modelNameToSchemaCache = Collections.unmodifiableMap(m);
@@ -1060,6 +1059,7 @@ public void setOpenAPI(OpenAPI openAPI) {
             once(LOGGER).warn(UNSUPPORTED_V310_SPEC_MSG);
         }
         this.openAPI = openAPI;
+        this.modelNameToSchemaCache = null;
         // Set global settings such that helper functions in ModelUtils can lookup the value
         // of the CLI option.
         ModelUtils.setDisallowAdditionalPropertiesIfNotPresent(getDisallowAdditionalPropertiesIfNotPresent());
@@ -7166,18 +7166,15 @@ public void updateCodegenPropertyEnum(CodegenProperty var) {
         }
 
         String varDataType = var.mostInnerItems != null ? var.mostInnerItems.dataType : var.dataType;
-        Optional<Schema> referencedSchema = ModelUtils.getSchemas(openAPI).entrySet().stream()
-                .filter(entry -> Objects.equals(varDataType, toModelName(entry.getKey())))
-                .map(Map.Entry::getValue)
-                .findFirst();
-        String dataType = (referencedSchema.isPresent()) ? getTypeDeclaration(referencedSchema.get()) : varDataType;
+        Schema referencedSchema = getModelNameToSchemaCache().get(varDataType);
+        String dataType = referencedSchema != null ? getTypeDeclaration(referencedSchema) : varDataType;
         List<EnumVarMap> enumVars = buildEnumVars(values, dataType);
         postProcessEnumVars(enumVars);
 
         // if "x-enum-varnames" or "x-enum-descriptions" defined, update varnames
         Map<String, Object> extensions = var.mostInnerItems != null ? var.mostInnerItems.getVendorExtensions() : var.getVendorExtensions();
-        if (referencedSchema.isPresent()) {
-            extensions = referencedSchema.get().getExtensions();
+        if (referencedSchema != null) {
+            extensions = referencedSchema.getExtensions();
         }
         updateEnumVarsWithExtensions(enumVars, extensions, dataType);
         allowableValues.put(ENUM_VARS, enumVars);