diff --git a/crates/web-sys/tests/wasm/response.rs b/crates/web-sys/tests/wasm/response.rs
index 40c893f5..5da87aec 100644
--- a/crates/web-sys/tests/wasm/response.rs
+++ b/crates/web-sys/tests/wasm/response.rs
@@ -1,4 +1,12 @@
+extern crate futures;
+extern crate js_sys;
+extern crate wasm_bindgen_futures;
+
+use futures::Future;
+use js_sys::{ArrayBuffer, DataView};
 use wasm_bindgen::prelude::*;
+use wasm_bindgen::JsCast;
+use wasm_bindgen_futures::JsFuture;
 use wasm_bindgen_test::*;
 use web_sys::Response;
 
@@ -8,9 +16,27 @@ extern "C" {
 }
 
 #[wasm_bindgen_test]
-fn test_response() {
+fn test_response_from_js() {
     let response = new_response();
     assert!(!response.ok());
     assert!(!response.redirected());
     assert_eq!(response.status(), 501);
 }
+
+#[wasm_bindgen_test(async)]
+fn test_response_from_bytes() -> impl Future<Item = (), Error = JsValue> {
+    let mut bytes: [u8; 3] = [1, 3, 5];
+    let response = Response::new_with_opt_u8_array(Some(&mut bytes)).unwrap();
+    assert!(response.ok());
+    assert_eq!(response.status(), 200);
+
+    let buf_promise = response.array_buffer().unwrap();
+    JsFuture::from(buf_promise).map(move |buf_val| {
+        assert!(buf_val.is_instance_of::<ArrayBuffer>());
+        let array_buf: ArrayBuffer = buf_val.dyn_into().unwrap();
+        let data_view = DataView::new(&array_buf, 0, bytes.len());
+        for (i, byte) in bytes.iter().enumerate() {
+            assert_eq!(&data_view.get_uint8(i), byte);
+        }
+    })
+}
diff --git a/crates/webidl/src/idl_type.rs b/crates/webidl/src/idl_type.rs
index 8d20eb13..6d3847d3 100644
--- a/crates/webidl/src/idl_type.rs
+++ b/crates/webidl/src/idl_type.rs
@@ -63,24 +63,26 @@ pub(crate) enum IdlType<'a> {
 
     Any,
     Void,
+
+    UnknownInterface(&'a str),
 }
 
 pub(crate) trait ToIdlType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>>;
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a>;
 }
 
 impl<'a> ToIdlType<'a> for UnionType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         let mut idl_types = Vec::with_capacity(self.body.list.len());
         for t in &self.body.list {
-            idl_types.push(t.to_idl_type(record)?);
+            idl_types.push(t.to_idl_type(record));
         }
-        Some(IdlType::Union(idl_types))
+        IdlType::Union(idl_types)
     }
 }
 
 impl<'a> ToIdlType<'a> for Type<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             Type::Single(t) => t.to_idl_type(record),
             Type::Union(t) => t.to_idl_type(record),
@@ -89,7 +91,7 @@ impl<'a> ToIdlType<'a> for Type<'a> {
 }
 
 impl<'a> ToIdlType<'a> for SingleType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             SingleType::Any(t) => t.to_idl_type(record),
             SingleType::NonAny(t) => t.to_idl_type(record),
@@ -98,7 +100,7 @@ impl<'a> ToIdlType<'a> for SingleType<'a> {
 }
 
 impl<'a> ToIdlType<'a> for NonAnyType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             NonAnyType::Promise(t) => t.to_idl_type(record),
             NonAnyType::Integer(t) => t.to_idl_type(record),
@@ -134,42 +136,36 @@ impl<'a> ToIdlType<'a> for NonAnyType<'a> {
 }
 
 impl<'a> ToIdlType<'a> for SequenceType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-        Some(IdlType::Sequence(Box::new(
-            self.generics.body.to_idl_type(record)?,
-        )))
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
+        IdlType::Sequence(Box::new(self.generics.body.to_idl_type(record)))
     }
 }
 
 impl<'a> ToIdlType<'a> for FrozenArrayType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-        Some(IdlType::FrozenArray(Box::new(
-            self.generics.body.to_idl_type(record)?,
-        )))
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
+        IdlType::FrozenArray(Box::new(self.generics.body.to_idl_type(record)))
     }
 }
 
 impl<'a, T: ToIdlType<'a>> ToIdlType<'a> for MayBeNull<T> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-        let inner_idl_type = self.type_.to_idl_type(record)?;
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
+        let inner_idl_type = self.type_.to_idl_type(record);
         if self.q_mark.is_some() {
-            Some(IdlType::Nullable(Box::new(inner_idl_type)))
+            IdlType::Nullable(Box::new(inner_idl_type))
         } else {
-            Some(inner_idl_type)
+            inner_idl_type
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for PromiseType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-        Some(IdlType::Promise(Box::new(
-            self.generics.body.to_idl_type(record)?,
-        )))
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
+        IdlType::Promise(Box::new(self.generics.body.to_idl_type(record)))
     }
 }
 
 impl<'a> ToIdlType<'a> for IntegerType {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             IntegerType::LongLong(t) => t.to_idl_type(record),
             IntegerType::Long(t) => t.to_idl_type(record),
@@ -179,37 +175,37 @@ impl<'a> ToIdlType<'a> for IntegerType {
 }
 
 impl<'a> ToIdlType<'a> for LongLongType {
-    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.unsigned.is_some() {
-            Some(IdlType::UnsignedLongLong)
+            IdlType::UnsignedLongLong
         } else {
-            Some(IdlType::LongLong)
+            IdlType::LongLong
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for LongType {
-    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.unsigned.is_some() {
-            Some(IdlType::UnsignedLong)
+            IdlType::UnsignedLong
         } else {
-            Some(IdlType::Long)
+            IdlType::Long
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for ShortType {
-    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.unsigned.is_some() {
-            Some(IdlType::UnsignedShort)
+            IdlType::UnsignedShort
         } else {
-            Some(IdlType::Short)
+            IdlType::Short
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for FloatingPointType {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             FloatingPointType::Float(t) => t.to_idl_type(record),
             FloatingPointType::Double(t) => t.to_idl_type(record),
@@ -218,36 +214,36 @@ impl<'a> ToIdlType<'a> for FloatingPointType {
 }
 
 impl<'a> ToIdlType<'a> for FloatType {
-    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.unrestricted.is_some() {
-            Some(IdlType::UnrestrictedFloat)
+            IdlType::UnrestrictedFloat
         } else {
-            Some(IdlType::Float)
+            IdlType::Float
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for DoubleType {
-    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.unrestricted.is_some() {
-            Some(IdlType::UnrestrictedDouble)
+            IdlType::UnrestrictedDouble
         } else {
-            Some(IdlType::Double)
+            IdlType::Double
         }
     }
 }
 
 impl<'a> ToIdlType<'a> for RecordType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-        Some(IdlType::Record(
-            Box::new(self.generics.body.0.to_idl_type(record)?),
-            Box::new(self.generics.body.2.to_idl_type(record)?),
-        ))
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
+        IdlType::Record(
+            Box::new(self.generics.body.0.to_idl_type(record)),
+            Box::new(self.generics.body.2.to_idl_type(record)),
+        )
     }
 }
 
 impl<'a> ToIdlType<'a> for StringType {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             StringType::Byte(t) => t.to_idl_type(record),
             StringType::DOM(t) => t.to_idl_type(record),
@@ -257,7 +253,7 @@ impl<'a> ToIdlType<'a> for StringType {
 }
 
 impl<'a> ToIdlType<'a> for UnionMemberType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             UnionMemberType::Single(t) => t.to_idl_type(record),
             UnionMemberType::Union(t) => t.to_idl_type(record),
@@ -266,7 +262,7 @@ impl<'a> ToIdlType<'a> for UnionMemberType<'a> {
 }
 
 impl<'a> ToIdlType<'a> for ConstType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             ConstType::Integer(t) => t.to_idl_type(record),
             ConstType::FloatingPoint(t) => t.to_idl_type(record),
@@ -279,7 +275,7 @@ impl<'a> ToIdlType<'a> for ConstType<'a> {
 }
 
 impl<'a> ToIdlType<'a> for ReturnType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         match self {
             ReturnType::Void(t) => t.to_idl_type(record),
             ReturnType::Type(t) => t.to_idl_type(record),
@@ -288,31 +284,31 @@ impl<'a> ToIdlType<'a> for ReturnType<'a> {
 }
 
 impl<'a> ToIdlType<'a> for AttributedType<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         self.type_.to_idl_type(record)
     }
 }
 
 impl<'a> ToIdlType<'a> for Identifier<'a> {
-    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
+    fn to_idl_type(&self, record: &FirstPassRecord<'a>) -> IdlType<'a> {
         if self.0 == "DOMTimeStamp" {
             // https://heycam.github.io/webidl/#DOMTimeStamp
-            Some(IdlType::UnsignedLongLong)
+            IdlType::UnsignedLongLong
         } else if let Some(idl_type) = record.typedefs.get(&self.0) {
             idl_type.to_idl_type(record)
         } else if record.interfaces.contains_key(self.0) {
-            Some(IdlType::Interface(self.0))
+            IdlType::Interface(self.0)
         } else if record.dictionaries.contains_key(self.0) {
-            Some(IdlType::Dictionary(self.0))
+            IdlType::Dictionary(self.0)
         } else if record.enums.contains_key(self.0) {
-            Some(IdlType::Enum(self.0))
+            IdlType::Enum(self.0)
         } else if record.callbacks.contains(self.0) {
-            Some(IdlType::Callback)
+            IdlType::Callback
         } else if let Some(data) = record.callback_interfaces.get(self.0) {
-            Some(IdlType::CallbackInterface {
+            IdlType::CallbackInterface {
                 name: self.0,
                 single_function: data.single_function,
-            })
+            }
         } else if self.0 == "WindowProxy" {
             // See this for more info:
             //
@@ -320,10 +316,10 @@ impl<'a> ToIdlType<'a> for Identifier<'a> {
             //
             // namely this seems to be "legalese" for "this is a `Window`", so
             // let's translate it as such.
-            Some(IdlType::Interface("Window"))
+            IdlType::Interface("Window")
         } else {
             warn!("Unrecognized type: {}", self.0);
-            None
+            IdlType::UnknownInterface(self.0)
         }
     }
 }
@@ -331,8 +327,8 @@ impl<'a> ToIdlType<'a> for Identifier<'a> {
 macro_rules! terms_to_idl_type {
     ($($t:tt => $r:tt)*) => ($(
         impl<'a> ToIdlType<'a> for term::$t {
-            fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> Option<IdlType<'a>> {
-                Some(IdlType::$r)
+            fn to_idl_type(&self, _record: &FirstPassRecord<'a>) -> IdlType<'a> {
+                IdlType::$r
             }
         }
     )*)
@@ -406,6 +402,7 @@ impl<'a> IdlType<'a> {
             IdlType::BufferSource => dst.push_str("buffer_source"),
 
             IdlType::Interface(name) => dst.push_str(&snake_case_ident(name)),
+            IdlType::UnknownInterface(name) => dst.push_str(&snake_case_ident(name)),
             IdlType::Dictionary(name) => dst.push_str(&snake_case_ident(name)),
             IdlType::Enum(name) => dst.push_str(&snake_case_ident(name)),
             IdlType::CallbackInterface { name, .. } => dst.push_str(&snake_case_ident(name)),
@@ -587,6 +584,7 @@ impl<'a> IdlType<'a> {
             }
             IdlType::Void => None,
             IdlType::Callback => js_sys("Function"),
+            IdlType::UnknownInterface(_) => None,
         }
     }
 
diff --git a/crates/webidl/src/lib.rs b/crates/webidl/src/lib.rs
index 3c7720f9..0c1bd020 100644
--- a/crates/webidl/src/lib.rs
+++ b/crates/webidl/src/lib.rs
@@ -353,7 +353,7 @@ impl<'src> FirstPassRecord<'src> {
         // use argument position now as we're just binding setters
         let ty = field
             .type_
-            .to_idl_type(self)?
+            .to_idl_type(self)
             .to_syn_type(TypePosition::Argument)?;
 
         // Slice types aren't supported because they don't implement
@@ -459,11 +459,7 @@ impl<'src> FirstPassRecord<'src> {
         self_name: &'src str,
         member: &'src weedle::interface::ConstMember<'src>,
     ) {
-        let idl_type = match member.const_type.to_idl_type(self) {
-            Some(idl_type) => idl_type,
-            None => return,
-        };
-
+        let idl_type = member.const_type.to_idl_type(self);
         let ty = match idl_type.to_syn_type(TypePosition::Return) {
             Some(ty) => ty,
             None => {
diff --git a/crates/webidl/src/util.rs b/crates/webidl/src/util.rs
index 0cbf684e..2acee7d6 100644
--- a/crates/webidl/src/util.rs
+++ b/crates/webidl/src/util.rs
@@ -336,7 +336,7 @@ impl<'src> FirstPassRecord<'src> {
     ) -> Option<backend::ast::ImportFunction> {
         let kind = backend::ast::OperationKind::Getter(Some(raw_ident(name)));
         let kind = self.import_function_kind(self_name, is_static, kind);
-        let ret = ty.to_idl_type(self)?;
+        let ret = ty.to_idl_type(self);
         self.create_one_function(
             &name,
             &snake_case_ident(name),
@@ -366,7 +366,7 @@ impl<'src> FirstPassRecord<'src> {
     ) -> Option<backend::ast::ImportFunction> {
         let kind = backend::ast::OperationKind::Setter(Some(raw_ident(name)));
         let kind = self.import_function_kind(self_name, is_static, kind);
-        let field_ty = field_ty.to_idl_type(self)?;
+        let field_ty = field_ty.to_idl_type(self);
         self.create_one_function(
             &name,
             &format!("set_{}", name).to_snake_case(),
@@ -431,10 +431,7 @@ impl<'src> FirstPassRecord<'src> {
                     );
                     signatures.push((signature, idl_args.clone()));
                 }
-                match arg.ty.to_idl_type(self) {
-                    Some(t) => idl_args.push(t),
-                    None => continue 'outer,
-                }
+                idl_args.push(arg.ty.to_idl_type(self));
             }
             signatures.push((signature, idl_args));
         }
@@ -517,10 +514,7 @@ impl<'src> FirstPassRecord<'src> {
             // TODO: overloads probably never change return types, so we should
             //       do this much earlier to avoid all the above work if
             //       possible.
-            let ret_ty = match signature.orig.ret.to_idl_type(self) {
-                Some(ty) => ty,
-                None => continue,
-            };
+            let ret_ty = signature.orig.ret.to_idl_type(self);
 
             let mut rust_name = snake_case_ident(name);
             let mut first = true;