diff --git a/plugins/node/opentelemetry-instrumentation-fastify/src/instrumentation.ts b/plugins/node/opentelemetry-instrumentation-fastify/src/instrumentation.ts
index fcaf3114e6..fd6aaa89c4 100644
--- a/plugins/node/opentelemetry-instrumentation-fastify/src/instrumentation.ts
+++ b/plugins/node/opentelemetry-instrumentation-fastify/src/instrumentation.ts
@@ -197,14 +197,14 @@ export class FastifyInstrumentation extends InstrumentationBase {
     };
   }
 
-  private _patchConstructor(
-    original: () => FastifyInstance
-  ): () => FastifyInstance {
+  private _patchConstructor(moduleExports: {
+    fastify: () => FastifyInstance;
+  }): () => FastifyInstance {
     const instrumentation = this;
     this._diag.debug('Patching fastify constructor function');
 
     function fastify(this: FastifyInstance, ...args: any) {
-      const app: FastifyInstance = original.apply(this, args);
+      const app: FastifyInstance = moduleExports.fastify.apply(this, args);
       app.addHook('onRequest', instrumentation._hookOnRequest());
       app.addHook('preHandler', instrumentation._hookPreHandler());