diff --git a/components/net_traits/request.rs b/components/net_traits/request.rs
index d8da3f1f002..18cbb7fa661 100644
--- a/components/net_traits/request.rs
+++ b/components/net_traits/request.rs
@@ -134,6 +134,14 @@ pub enum CorsSettings {
     UseCredentials,
 }
 
+/// [Parser Metadata](https://fetch.spec.whatwg.org/#concept-request-parser-metadata)
+#[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize)]
+pub enum ParserMetadata {
+    Default,
+    ParserInserted,
+    NotParserInserted,
+}
+
 #[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct RequestBuilder {
     #[serde(
@@ -169,6 +177,7 @@ pub struct RequestBuilder {
     pub integrity_metadata: String,
     // to keep track of redirects
     pub url_list: Vec<ServoUrl>,
+    pub parser_metadata: ParserMetadata,
 }
 
 impl RequestBuilder {
@@ -194,6 +203,7 @@ impl RequestBuilder {
             redirect_mode: RedirectMode::Follow,
             integrity_metadata: "".to_owned(),
             url_list: vec![],
+            parser_metadata: ParserMetadata::Default,
         }
     }
 
@@ -295,6 +305,11 @@ impl RequestBuilder {
         self
     }
 
+    pub fn parser_metadata(mut self, parser_metadata: ParserMetadata) -> RequestBuilder {
+        self.parser_metadata = parser_metadata;
+        self
+    }
+
     pub fn build(self) -> Request {
         let mut request = Request::new(
             self.url.clone(),
@@ -323,6 +338,7 @@ impl RequestBuilder {
         request.redirect_count = url_list.len() as u32 - 1;
         request.url_list = url_list;
         request.integrity_metadata = self.integrity_metadata;
+        request.parser_metadata = self.parser_metadata;
         request
     }
 }
@@ -388,6 +404,8 @@ pub struct Request {
     pub redirect_count: u32,
     /// <https://fetch.spec.whatwg.org/#concept-request-response-tainting>
     pub response_tainting: ResponseTainting,
+    /// <https://fetch.spec.whatwg.org/#concept-request-parser-metadata>
+    pub parser_metadata: ParserMetadata,
 }
 
 impl Request {
@@ -417,6 +435,7 @@ impl Request {
             redirect_mode: RedirectMode::Follow,
             integrity_metadata: String::new(),
             url_list: vec![url],
+            parser_metadata: ParserMetadata::Default,
             redirect_count: 0,
             response_tainting: ResponseTainting::Basic,
         }
diff --git a/components/script/dom/dedicatedworkerglobalscope.rs b/components/script/dom/dedicatedworkerglobalscope.rs
index 0ca5280849d..75d4b272834 100644
--- a/components/script/dom/dedicatedworkerglobalscope.rs
+++ b/components/script/dom/dedicatedworkerglobalscope.rs
@@ -38,7 +38,8 @@ use js::jsapi::{JSAutoRealm, JSContext};
 use js::jsval::UndefinedValue;
 use js::rust::HandleValue;
 use msg::constellation_msg::{PipelineId, TopLevelBrowsingContextId};
-use net_traits::request::{CredentialsMode, Destination, Referrer, RequestBuilder};
+use net_traits::request::{CredentialsMode, Destination, ParserMetadata};
+use net_traits::request::{Referrer, RequestBuilder, RequestMode};
 use net_traits::IpcSend;
 use script_traits::{TimerEvent, TimerSource, WorkerGlobalScopeInit, WorkerScriptLoadOrigin};
 use servo_rand::random;
@@ -321,7 +322,9 @@ impl DedicatedWorkerGlobalScope {
 
                 let request = RequestBuilder::new(worker_url.clone())
                     .destination(Destination::Worker)
-                    .credentials_mode(CredentialsMode::Include)
+                    .mode(RequestMode::SameOrigin)
+                    .credentials_mode(CredentialsMode::CredentialsSameOrigin)
+                    .parser_metadata(ParserMetadata::NotParserInserted)
                     .use_url_credentials(true)
                     .pipeline_id(pipeline_id)
                     .referrer(referrer)
diff --git a/components/script/dom/serviceworkerglobalscope.rs b/components/script/dom/serviceworkerglobalscope.rs
index f7eee199f93..c2b3eab5dc8 100644
--- a/components/script/dom/serviceworkerglobalscope.rs
+++ b/components/script/dom/serviceworkerglobalscope.rs
@@ -32,7 +32,7 @@ use ipc_channel::router::ROUTER;
 use js::jsapi::{JSAutoRealm, JSContext, JS_AddInterruptCallback};
 use js::jsval::UndefinedValue;
 use msg::constellation_msg::PipelineId;
-use net_traits::request::{CredentialsMode, Destination, Referrer, RequestBuilder};
+use net_traits::request::{CredentialsMode, Destination, ParserMetadata, Referrer, RequestBuilder};
 use net_traits::{CustomResponseMediator, IpcSend};
 use script_traits::{
     ScopeThings, ServiceWorkerMsg, TimerEvent, WorkerGlobalScopeInit, WorkerScriptLoadOrigin,
@@ -290,6 +290,7 @@ impl ServiceWorkerGlobalScope {
                 let request = RequestBuilder::new(script_url.clone())
                     .destination(Destination::ServiceWorker)
                     .credentials_mode(CredentialsMode::Include)
+                    .parser_metadata(ParserMetadata::NotParserInserted)
                     .use_url_credentials(true)
                     .pipeline_id(pipeline_id)
                     .referrer(referrer)
diff --git a/components/script/dom/workerglobalscope.rs b/components/script/dom/workerglobalscope.rs
index cf0bab5967c..3ea44c99936 100644
--- a/components/script/dom/workerglobalscope.rs
+++ b/components/script/dom/workerglobalscope.rs
@@ -43,7 +43,9 @@ use js::jsval::UndefinedValue;
 use js::panic::maybe_resume_unwind;
 use js::rust::{HandleValue, ParentRuntime};
 use msg::constellation_msg::PipelineId;
-use net_traits::request::{CredentialsMode, Destination, RequestBuilder as NetRequestInit};
+use net_traits::request::{
+    CredentialsMode, Destination, ParserMetadata, RequestBuilder as NetRequestInit,
+};
 use net_traits::IpcSend;
 use script_traits::WorkerGlobalScopeInit;
 use script_traits::{TimerEvent, TimerEventId};
@@ -224,6 +226,7 @@ impl WorkerGlobalScopeMethods for WorkerGlobalScope {
             let request = NetRequestInit::new(url.clone())
                 .destination(Destination::Script)
                 .credentials_mode(CredentialsMode::Include)
+                .parser_metadata(ParserMetadata::NotParserInserted)
                 .use_url_credentials(true)
                 .origin(global_scope.origin().immutable().clone())
                 .pipeline_id(Some(self.upcast::<GlobalScope>().pipeline_id()))
diff --git a/components/script/fetch.rs b/components/script/fetch.rs
index 8f0319f4443..e7011707227 100644
--- a/components/script/fetch.rs
+++ b/components/script/fetch.rs
@@ -124,6 +124,7 @@ fn request_init_from_request(request: NetTraitsRequest) -> RequestBuilder {
         redirect_mode: request.redirect_mode,
         integrity_metadata: "".to_owned(),
         url_list: vec![],
+        parser_metadata: request.parser_metadata,
     }
 }
 
diff --git a/tests/wpt/metadata/workers/constructors/Worker/same-origin.html.ini b/tests/wpt/metadata/workers/constructors/Worker/same-origin.html.ini
index 8c2533c6d98..de990d5d1e6 100644
--- a/tests/wpt/metadata/workers/constructors/Worker/same-origin.html.ini
+++ b/tests/wpt/metadata/workers/constructors/Worker/same-origin.html.ini
@@ -1,3 +1,9 @@
 [same-origin.html]
   type: testharness
-  disabled: intermittent failures
+  expected: TIMEOUT
+  [unsupported_scheme]
+    expected: FAIL
+
+  [about_blank]
+    expected: TIMEOUT
+