diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
index fb131f00499..696bf349ca5 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
@@ -502,7 +502,7 @@ public class TypeScriptClientCodegen extends AbstractTypeScriptClientCodegen imp
 
     @Override
     protected void addAdditionPropertiesToCodeGenModel(CodegenModel codegenModel, Schema schema) {
-        codegenModel.additionalPropertiesType = getTypeDeclaration((Schema) schema.getAdditionalProperties());
+        codegenModel.additionalPropertiesType = getSchemaType(ModelUtils.getAdditionalProperties(schema));
         addImport(codegenModel, codegenModel.additionalPropertiesType);
     }