diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
index ffb94b71742..a57a9f991e9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
@@ -413,7 +413,9 @@ public abstract class AbstractTypeScriptClientCodegen extends DefaultCodegen imp
             setParamNaming((String) additionalProperties.get(CodegenConstants.PARAM_NAMING));
         }
 
-        setSupportsES6(convertPropertyToBooleanAndWriteBack(CodegenConstants.SUPPORTS_ES6));
+        if (additionalProperties.containsKey(CodegenConstants.SUPPORTS_ES6)) {
+            setSupportsES6(convertPropertyToBooleanAndWriteBack(CodegenConstants.SUPPORTS_ES6));
+        }
 
         if (additionalProperties.containsKey(NULL_SAFE_ADDITIONAL_PROPS)) {
             setNullSafeAdditionalProps(Boolean.valueOf(additionalProperties.get(NULL_SAFE_ADDITIONAL_PROPS).toString()));