diff --git a/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp b/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
index a5aa69790a..7be2cdada4 100644
--- a/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
+++ b/Userland/Libraries/LibWeb/Streams/AbstractOperations.cpp
@@ -2734,6 +2734,15 @@ void transform_stream_default_controller_clear_algorithms(TransformStreamDefault
     controller.set_flush_algorithm({});
 }
 
+// https://streams.spec.whatwg.org/#transform-stream-default-controller-error
+WebIDL::ExceptionOr<void> transform_stream_default_controller_error(TransformStreamDefaultController& controller, JS::Value error)
+{
+    // 1. Perform ! TransformStreamError(controller.[[stream]], e).
+    TRY(transform_stream_error(*controller.stream(), error));
+
+    return {};
+}
+
 // https://streams.spec.whatwg.org/#transform-stream-error
 WebIDL::ExceptionOr<void> transform_stream_error(TransformStream& stream, JS::Value error)
 {
diff --git a/Userland/Libraries/LibWeb/Streams/AbstractOperations.h b/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
index 6144b63107..36ce19502e 100644
--- a/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
+++ b/Userland/Libraries/LibWeb/Streams/AbstractOperations.h
@@ -133,6 +133,7 @@ WebIDL::ExceptionOr<void> writable_stream_default_controller_process_write(Writa
 WebIDL::ExceptionOr<void> writable_stream_default_controller_write(WritableStreamDefaultController&, JS::Value chunk, JS::Value chunk_size);
 
 void transform_stream_default_controller_clear_algorithms(TransformStreamDefaultController&);
+WebIDL::ExceptionOr<void> transform_stream_default_controller_error(TransformStreamDefaultController&, JS::Value error);
 WebIDL::ExceptionOr<void> transform_stream_error(TransformStream&, JS::Value error);
 WebIDL::ExceptionOr<void> transform_stream_error_writable_and_unblock_write(TransformStream&, JS::Value error);
 WebIDL::ExceptionOr<void> transform_stream_set_backpressure(TransformStream&, bool backpressure);