1 files changed, 13 insertions, 3 deletions
diff --git a/src/js/node/http.ts b/src/js/node/http.ts
index 563cb8c46..42388b32e 100644
--- a/src/js/node/http.ts
+++ b/src/js/node/http.ts
@@ -957,6 +957,7 @@ export class OutgoingMessage extends Writable {
   }
 }
 
+let OriginalWriteHeadFn, OriginalImplicitHeadFn;
 export class ServerResponse extends Writable {
   declare _writableState: any;
 
@@ -1055,14 +1056,20 @@ export class ServerResponse extends Writable {
     );
   }
 
+  #drainHeadersIfObservable() {
+    if (this._implicitHeader === OriginalImplicitHeadFn && this.writeHead === OriginalWriteHeadFn) {
+      return;
+    }
+
+    this._implicitHeader();
+  }
+
   _final(callback) {
     if (!this.headersSent) {
       var data = this.#firstWrite || "";
       this.#firstWrite = undefined;
       this.#finished = true;
-      if (this.writeHead !== Object.getPrototypeOf(this).writeHead) {
-        this._implicitHeader();
-      }
+      this.#drainHeadersIfObservable();
       this._reply(
         new Response(data, {
           headers: this.#headers,
@@ -1181,6 +1188,9 @@ export class ServerResponse extends Writable {
   }
 }
 
+OriginalWriteHeadFn = ServerResponse.prototype.writeHead;
+OriginalImplicitHeadFn = ServerResponse.prototype._implicitHeader;
+
 export class ClientRequest extends OutgoingMessage {
   #timeout;
   #res: IncomingMessage | null = null;