diff --git a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-do/index.ts b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-do/index.ts
index 22551809d210..6ec278fc9ace 100644
--- a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-do/index.ts
+++ b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-do/index.ts
@@ -8,7 +8,7 @@ interface Env {
 }
 
 class MyDurableObjectBase extends DurableObject<Env> {
-  async fetch(request: Request) {
+  async fetch(_request: Request) {
     return new Response('DO is fine');
   }
 }
diff --git a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-service-binding/index-sub-worker.ts b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-service-binding/index-sub-worker.ts
index 06c79931b880..95de55198929 100644
--- a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-service-binding/index-sub-worker.ts
+++ b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/worker-service-binding/index-sub-worker.ts
@@ -5,7 +5,7 @@ interface Env {
 }
 
 const myWorker = {
-  async fetch(request: Request) {
+  async fetch(_request: Request) {
     return new Response('Hello from another worker!');
   },
 };
diff --git a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/workflow-do/index.ts b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/workflow-do/index.ts
index 06c846afc378..0ffd77866e1f 100644
--- a/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/workflow-do/index.ts
+++ b/dev-packages/cloudflare-integration-tests/suites/tracing/propagation/workflow-do/index.ts
@@ -9,7 +9,7 @@ interface Env {
 }
 
 class MyDurableObjectBase extends DurableObject<Env> {
-  async fetch(request: Request) {
+  async fetch(_request: Request) {
     return new Response('DO is fine');
   }
 }
diff --git a/packages/core/src/fetch.ts b/packages/core/src/fetch.ts
index 0de9685528c3..21a89b15c825 100644
--- a/packages/core/src/fetch.ts
+++ b/packages/core/src/fetch.ts
@@ -287,11 +287,10 @@ export function _INTERNAL_getTracingHeadersForFetchRequest(
       'sentry-trace': string;
       baggage: string | undefined;
       traceparent?: string;
-    } = {
-      ...originalHeaders,
+    } = Object.assign({}, originalHeaders, {
       'sentry-trace': (existingSentryTraceHeader as string | undefined) ?? sentryTrace,
       baggage: newBaggageHeaders.length > 0 ? newBaggageHeaders.join(',') : undefined,
-    };
+    });
 
     if (propagateTraceparent && traceparent && !existingTraceparentHeader) {
       newHeaders.traceparent = traceparent;