diff --git a/components/script/dom/bindings/structuredclone.rs b/components/script/dom/bindings/structuredclone.rs
index ed3cf6aa6e2..b3a9df32695 100644
--- a/components/script/dom/bindings/structuredclone.rs
+++ b/components/script/dom/bindings/structuredclone.rs
@@ -87,7 +87,7 @@ unsafe fn write_blob(blob: Root<Blob>,
                      -> Result<(), ()> {
     let blob_vec = try!(blob.get_bytes());
     let blob_length = blob_vec.len();
-    let type_string_bytes = blob.get_type_string().as_bytes().to_vec();
+    let type_string_bytes = blob.type_string().as_bytes().to_vec();
     let type_string_length = type_string_bytes.len();
     assert!(JS_WriteUint32Pair(w, StructuredCloneTags::DomBlob as u32, 0));
     write_length(w, blob_length);
diff --git a/components/script/dom/blob.rs b/components/script/dom/blob.rs
index d8ed5fa1b64..cb61ced9e3a 100644
--- a/components/script/dom/blob.rs
+++ b/components/script/dom/blob.rs
@@ -164,7 +164,7 @@ impl Blob {
     }
 
     /// Get a copy of the type_string
-    pub fn get_type_string(&self) -> String {
+    pub fn type_string(&self) -> String {
         self.type_string.clone()
     }
 
diff --git a/components/script/dom/formdata.rs b/components/script/dom/formdata.rs
index 2b8ca8f4d46..af4c692e7d9 100644
--- a/components/script/dom/formdata.rs
+++ b/components/script/dom/formdata.rs
@@ -7,6 +7,7 @@ use dom::bindings::codegen::Bindings::FormDataBinding::FormDataMethods;
 use dom::bindings::codegen::Bindings::FormDataBinding::FormDataWrap;
 use dom::bindings::codegen::UnionTypes::FileOrUSVString;
 use dom::bindings::error::Fallible;
+use dom::bindings::inheritance::Castable;
 use dom::bindings::iterable::Iterable;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::{DomObject, Reflector, reflect_dom_object};
@@ -79,7 +80,7 @@ impl FormDataMethods for FormData {
         let datum = FormDatum {
             ty: DOMString::from("file"),
             name: DOMString::from(name.0.clone()),
-            value: FormDatumValue::File(Root::from_ref(&*self.get_file(blob, filename))),
+            value: FormDatumValue::File(Root::from_ref(&*self.create_an_entry(blob, filename))),
         };
 
         let mut data = self.data.borrow_mut();
@@ -137,7 +138,7 @@ impl FormDataMethods for FormData {
         self.data.borrow_mut().insert(LocalName::from(name.0.clone()), vec![FormDatum {
             ty: DOMString::from("file"),
             name: DOMString::from(name.0),
-            value: FormDatumValue::File(Root::from_ref(&*self.get_file(blob, filename))),
+            value: FormDatumValue::File(Root::from_ref(&*self.create_an_entry(blob, filename))),
         }]);
     }
 
@@ -145,15 +146,18 @@ impl FormDataMethods for FormData {
 
 
 impl FormData {
-    fn get_file(&self, blob: &Blob, opt_filename: Option<USVString>) -> Root<File> {
+    // https://xhr.spec.whatwg.org/#create-an-entry
+    // Steps 3-4.
+    fn create_an_entry(&self, blob: &Blob, opt_filename: Option<USVString>) -> Root<File> {
         let name = match opt_filename {
             Some(filename) => DOMString::from(filename.0),
+            None if blob.downcast::<File>().is_none() => DOMString::from("blob"),
             None => DOMString::from(""),
         };
 
         let bytes = blob.get_bytes().unwrap_or(vec![]);
 
-        File::new(&self.global(), BlobImpl::new_from_bytes(bytes), name, None, "")
+        File::new(&self.global(), BlobImpl::new_from_bytes(bytes), name, None, &blob.type_string())
     }
 
     pub fn datums(&self) -> Vec<FormDatum> {
diff --git a/tests/wpt/metadata/XMLHttpRequest/formdata-blob.htm.ini b/tests/wpt/metadata/XMLHttpRequest/formdata-blob.htm.ini
deleted file mode 100644
index 32cb3afc3c5..00000000000
--- a/tests/wpt/metadata/XMLHttpRequest/formdata-blob.htm.ini
+++ /dev/null
@@ -1,8 +0,0 @@
-[formdata-blob.htm]
-  type: testharness
-  [formdata with blob]
-    expected: FAIL
-
-  [formdata with named blob]
-    expected: FAIL
-