diff --git a/packages/core/src/helpers.ts b/packages/core/src/helpers.ts
index fffd57154..18e5db325 100644
--- a/packages/core/src/helpers.ts
+++ b/packages/core/src/helpers.ts
@@ -253,7 +253,7 @@ export default class Helpers implements Resolver {
      * Helper function to validate an ExposedThingInit
      */
     public static validateExposedThingInit(data: ExposedThingInit): { valid: boolean; errors?: string } {
-        if (data["@type"] === "tm:ThingModel" || ThingModelHelpers.isThingModel(data)) {
+        if (data["@type"] === "tm:ThingModel" || ThingModelHelpers.isThingModel(data) === true) {
             return {
                 valid: false,
                 errors: "ThingModel declaration is not supported",