diff --git a/src/core/hiwire.c b/src/core/hiwire.c
index 226d9960c..7c855da2b 100644
--- a/src/core/hiwire.c
+++ b/src/core/hiwire.c
@@ -19,11 +19,15 @@ const JsRef Js_null = ((JsRef)(8));
 const JsRef Js_novalue = ((JsRef)(1000));
 
 JsRef
-hiwire_bool(bool boolean)
+hiwire_from_bool(bool boolean)
 {
   return boolean ? Js_true : Js_false;
 }
 
+EM_JS(bool, hiwire_to_bool, (JsRef val), {
+  return !!Module.hiwire.get_value(val);
+});
+
 EM_JS_NUM(int, hiwire_init, (), {
   let _hiwire = {
     objects : new Map(),
@@ -49,6 +53,7 @@ EM_JS_NUM(int, hiwire_init, (), {
   _hiwire.objects.set(Module.hiwire.JSNULL, null);
   _hiwire.objects.set(Module.hiwire.TRUE, true);
   _hiwire.objects.set(Module.hiwire.FALSE, false);
+  let hiwire_next_permanent = Module.hiwire.FALSE + 2;
 
 #ifdef DEBUG_F
   Module.hiwire._hiwire = _hiwire;
@@ -83,7 +88,20 @@ EM_JS_NUM(int, hiwire_init, (), {
     return idval;
   };
 
-  Module.hiwire.num_keys = function() { return _hiwire.objects.size; };
+  Module.hiwire.intern_object = function(obj)
+  {
+    let id = hiwire_next_permanent;
+    hiwire_next_permanent += 2;
+    _hiwire.objects.set(id, obj);
+    return id;
+  };
+
+  // for testing purposes.
+  Module.hiwire.num_keys = function(){
+    // clang-format off
+    return Array.from(_hiwire.objects.keys()).filter((x) => x % 2).length
+    // clang-format on
+  };
 
   Module.hiwire.get_value = function(idval)
   {
@@ -216,6 +234,20 @@ EM_JS_NUM(int, hiwire_init, (), {
   return 0;
 });
 
+EM_JS_REF(JsRef, JsString_InternFromCString, (const char* str), {
+  let jsstring = UTF8ToString(str);
+  return Module.hiwire.intern_object(jsstring);
+})
+
+JsRef
+JsString_FromId(Js_Identifier* id)
+{
+  if (!id->object) {
+    id->object = JsString_InternFromCString(id->string);
+  }
+  return id->object;
+}
+
 EM_JS_REF(JsRef, hiwire_incref, (JsRef idval), {
   // clang-format off
   if ((idval & 1) === 0) {
@@ -428,44 +460,121 @@ hiwire_call_va(JsRef idobj, ...)
   return idresult;
 }
 
-EM_JS_REF(JsRef,
-          hiwire_call_bound,
-          (JsRef idfunc, JsRef idthis, JsRef idargs),
-          {
-            let func = Module.hiwire.get_value(idfunc);
-            let this_;
-            // clang-format off
-            if (idthis === 0) {
-              // clang-format on
-              this_ = null;
-            } else {
-              this_ = Module.hiwire.get_value(idthis);
-            }
-            let args = Module.hiwire.get_value(idargs);
-            return Module.hiwire.new_value(func.apply(this_, args));
-          });
+EM_JS_REF(JsRef, hiwire_call_OneArg, (JsRef idfunc, JsRef idarg), {
+  let jsfunc = Module.hiwire.get_value(idfunc);
+  let jsarg = Module.hiwire.get_value(idarg);
+  return Module.hiwire.new_value(jsfunc(jsarg));
+});
 
+// clang-format off
 EM_JS_REF(JsRef,
-          hiwire_call_member,
-          (JsRef idobj, const char* ptrname, JsRef idargs),
-          {
-            let jsobj = Module.hiwire.get_value(idobj);
-            let jsname = UTF8ToString(ptrname);
-            let jsargs = Module.hiwire.get_value(idargs);
-            return Module.hiwire.new_value(jsobj[jsname](... jsargs));
-          });
+hiwire_call_bound,
+(JsRef idfunc, JsRef idthis, JsRef idargs),
+{
+  let func = Module.hiwire.get_value(idfunc);
+  let this_;
+  if (idthis === 0) {
+    this_ = null;
+  } else {
+    this_ = Module.hiwire.get_value(idthis);
+  }
+  let args = Module.hiwire.get_value(idargs);
+  return Module.hiwire.new_value(func.apply(this_, args));
+});
+// clang-format on
+
+EM_JS_NUM(int, hiwire_HasMethod, (JsRef obj_id, JsRef name), {
+  // clang-format off
+  let obj = Module.hiwire.get_value(obj_id);
+  return obj && typeof obj[Module.hiwire.get_value(name)] === "function";
+  // clang-format on
+})
+
+int
+hiwire_HasMethodId(JsRef obj, Js_Identifier* name)
+{
+  JsRef name_ref = JsString_FromId(name);
+  if (name_ref == NULL) {
+    return -1;
+  }
+  return hiwire_HasMethod(obj, name_ref);
+}
+
+// clang-format off
+EM_JS_REF(
+JsRef,
+hiwire_CallMethodString,
+(JsRef idobj, const char* name, JsRef idargs),
+{
+  let jsobj = Module.hiwire.get_value(idobj);
+  let jsname = UTF8ToString(name);
+  let jsargs = Module.hiwire.get_value(idargs);
+  return Module.hiwire.new_value(jsobj[jsname](...jsargs));
+});
+// clang-format on
+
+EM_JS_REF(JsRef, hiwire_CallMethod, (JsRef idobj, JsRef name, JsRef idargs), {
+  let jsobj = Module.hiwire.get_value(idobj);
+  let jsname = Module.hiwire.get_value(name);
+  let jsargs = Module.hiwire.get_value(idargs);
+  return Module.hiwire.new_value(jsobj[jsname](... jsargs));
+});
+
+// clang-format off
+EM_JS_REF(
+JsRef,
+hiwire_CallMethod_OneArg,
+(JsRef idobj, JsRef name, JsRef idarg),
+{
+  let jsobj = Module.hiwire.get_value(idobj);
+  let jsname = Module.hiwire.get_value(name);
+  let jsarg = Module.hiwire.get_value(idarg);
+  return Module.hiwire.new_value(jsobj[jsname](jsarg));
+});
+// clang-format on
 
 JsRef
-hiwire_call_member_va(JsRef idobj, const char* ptrname, ...)
+hiwire_CallMethodId(JsRef idobj, Js_Identifier* name_id, JsRef idargs)
+{
+  JsRef name_ref = JsString_FromId(name_id);
+  if (name_ref == NULL) {
+    return NULL;
+  }
+  return hiwire_CallMethod(idobj, name_ref, idargs);
+}
+
+JsRef
+hiwire_CallMethodString_va(JsRef idobj, const char* ptrname, ...)
 {
   va_list args;
   va_start(args, ptrname);
   JsRef idargs = convert_va_args(args);
-  JsRef idresult = hiwire_call_member(idobj, ptrname, idargs);
+  JsRef idresult = hiwire_CallMethodString(idobj, ptrname, idargs);
   hiwire_decref(idargs);
   return idresult;
 }
 
+JsRef
+hiwire_CallMethodId_va(JsRef idobj, Js_Identifier* name, ...)
+{
+  va_list args;
+  va_start(args, name);
+  JsRef idargs = convert_va_args(args);
+  JsRef idresult = hiwire_CallMethodId(idobj, name, idargs);
+  hiwire_decref(idargs);
+  return idresult;
+}
+
+JsRef
+hiwire_CallMethodId_OneArg(JsRef obj, Js_Identifier* name, JsRef arg)
+{
+  JsRef name_ref = JsString_FromId(name);
+  if (name_ref == NULL) {
+    return NULL;
+  }
+  return hiwire_CallMethod_OneArg(obj, name_ref, arg);
+}
+
 EM_JS_REF(JsRef, hiwire_construct, (JsRef idobj, JsRef idargs), {
   let jsobj = Module.hiwire.get_value(idobj);
   let jsargs = Module.hiwire.get_value(idargs);
@@ -510,84 +619,6 @@ EM_JS_NUM(bool, hiwire_get_bool, (JsRef idobj), {
   // clang-format on
 });
 
-EM_JS_NUM(bool, hiwire_has_has_method, (JsRef idobj), {
-  // clang-format off
-  let obj = Module.hiwire.get_value(idobj);
-  return obj && typeof obj.has === "function";
-  // clang-format on
-});
-
-EM_JS_NUM(bool, hiwire_call_has_method, (JsRef idobj, JsRef idkey), {
-  // clang-format off
-  let obj = Module.hiwire.get_value(idobj);
-  let key = Module.hiwire.get_value(idkey);
-  return obj.has(key);
-  // clang-format on
-});
-
-EM_JS_NUM(bool, hiwire_has_includes_method, (JsRef idobj), {
-  // clang-format off
-  let obj = Module.hiwire.get_value(idobj);
-  return obj && typeof obj.includes === "function";
-  // clang-format on
-});
-
-EM_JS_NUM(bool, hiwire_call_includes_method, (JsRef idobj, JsRef idval), {
-  let obj = Module.hiwire.get_value(idobj);
-  let val = Module.hiwire.get_value(idval);
-  return obj.includes(val);
-});
-
-EM_JS_NUM(bool, hiwire_has_get_method, (JsRef idobj), {
-  // clang-format off
-  let obj = Module.hiwire.get_value(idobj);
-  return obj && typeof obj.get === "function";
-  // clang-format on
-});
-
-EM_JS_REF(JsRef, hiwire_call_get_method, (JsRef idobj, JsRef idkey), {
-  let obj = Module.hiwire.get_value(idobj);
-  let key = Module.hiwire.get_value(idkey);
-  let result = obj.get(key);
-  // clang-format off
-  if (result === undefined) {
-    // Try to distinguish between undefined and missing:
-    // If the object has a "has" method and it returns false for this key, the
-    // key is missing. Otherwise, assume key present and value was undefined.
-    // TODO: in absence of a "has" method, should we return None or KeyError?
-    if (obj.has && typeof obj.has === "function" && !obj.has(key)) {
-      return ERROR_REF;
-    }
-  }
-  // clang-format on
-  return Module.hiwire.new_value(result);
-});
-
-EM_JS_NUM(bool, hiwire_has_set_method, (JsRef idobj), {
-  // clang-format off
-  let obj = Module.hiwire.get_value(idobj);
-  return obj && typeof obj.set === "function";
-  // clang-format on
-});
-
-EM_JS_NUM(errcode,
-          hiwire_call_set_method,
-          (JsRef idobj, JsRef idkey, JsRef idval),
-          {
-            let obj = Module.hiwire.get_value(idobj);
-            let key = Module.hiwire.get_value(idkey);
-            let val = Module.hiwire.get_value(idval);
-            let result = obj.set(key, val);
-          });
-
-EM_JS_NUM(errcode, hiwire_call_delete_method, (JsRef idobj, JsRef idkey), {
-  let obj = Module.hiwire.get_value(idobj);
-  let key = Module.hiwire.get_value(idkey);
-  if (!obj.delete(key)) {
-    return -1;
-  }
-});
-
 EM_JS_NUM(bool, hiwire_is_pyproxy, (JsRef idobj), {
   return Module.isPyProxy(Module.hiwire.get_value(idobj));
 });
diff --git a/src/core/hiwire.h b/src/core/hiwire.h
index 945e68018..cb3797469 100644
--- a/src/core/hiwire.h
+++ b/src/core/hiwire.h
@@ -47,6 +47,25 @@ extern const JsRef Js_null;
 // For when the return value would be Option<JsRef>
 extern const JsRef Js_novalue;
 
+// A mechanism for handling static Javascript strings from C
+// This is copied from the Python mechanism for handling static Python strings
+// from C See the Python definition here:
+// https://github.com/python/cpython/blob/24da544014f78e6f1440d5ce5c2d14794a020340/Include/cpython/object.h#L37
+
+typedef struct Js_Identifier
+{
+  const char* string;
+  JsRef object;
+} Js_Identifier;
+
+#define Js_static_string_init(value)                                           \
+  {                                                                            \
+    .string = value, .object = NULL                                            \
+  }
+#define Js_static_string(varname, value)                                       \
+  static Js_Identifier varname = Js_static_string_init(value)
+#define Js_IDENTIFIER(varname) Js_static_string(JsId_##varname, #varname)
+
 #define hiwire_CLEAR(x)                                                        \
   do {                                                                         \
     hiwire_decref(x);                                                          \
@@ -150,7 +169,13 @@ hiwire_string_ascii(const char* ptr);
  * Returns: "New" reference
  */
 JsRef
-hiwire_bool(bool boolean);
+hiwire_from_bool(bool boolean);
+
+/**
+ * Convert value to C boolean
+ */
+bool
+hiwire_to_bool(JsRef value);
 
 bool
 JsArray_Check(JsRef idobj);
@@ -230,7 +255,7 @@ JsRef
 JsObject_Dir(JsRef idobj);
 
 /**
- * Call a function
+ * Call a js function
  *
  * idargs is a hiwire Array containing the arguments.
  *
@@ -238,6 +263,12 @@ JsObject_Dir(JsRef idobj);
 JsRef
 hiwire_call(JsRef idobj, JsRef idargs);
 
+/**
+ * Call a js function with one argument
+ */
+JsRef
+hiwire_call_OneArg(JsRef idobj, JsRef idarg);
+
 /**
  * Call a function
  *
@@ -251,28 +282,61 @@ hiwire_call_va(JsRef idobj, ...);
 JsRef
 hiwire_call_bound(JsRef idfunc, JsRef idthis, JsRef idargs);
 
-/**
- * Call a member function.
- *
- * ptrname is the member name, as a null-terminated UTF8.
- *
- * idargs is a hiwire Array containing the arguments.
- *
- */
-JsRef
-hiwire_call_member(JsRef idobj, const char* ptrname, JsRef idargs);
+int
+hiwire_HasMethod(JsRef obj, JsRef name);
+
+int
+hiwire_HasMethodId(JsRef obj, Js_Identifier* name);
 
 /**
- * Call a member function.
- *
- * ptrname is the member name, as a null-terminated UTF8.
- *
- * Arguments are specified as a NULL-terminated variable arguments list of
- * JsRefs.
+ * name is the method name, as null-terminated UTF8.
+ * args is an Array containing the arguments.
  *
  */
 JsRef
-hiwire_call_member_va(JsRef idobj, const char* ptrname, ...);
+hiwire_CallMethodString(JsRef obj, const char* name, JsRef args);
+
+/**
+ * name is the method name, as null-terminated UTF8.
+ * arg is the argument
+ */
+JsRef
+hiwire_CallMethodString_OneArg(JsRef obj, const char* name, JsRef arg);
+
+/**
+ * name is the method name, as null-terminated UTF8.
+ * Arguments are specified as a NULL-terminated variable arguments list of
+ * JsRefs.
+ */
+JsRef
+hiwire_CallMethodString_va(JsRef obj, const char* name, ...);
+
+JsRef
+hiwire_CallMethod(JsRef obj, JsRef name, JsRef args);
+
+JsRef
+hiwire_CallMethod_OneArg(JsRef obj, JsRef name, JsRef arg);
+
+JsRef
+hiwire_CallMethod_va(JsRef obj, JsRef name, ...);
+
+/**
+ * name is the method name, as a Js_Identifier
+ * args is a hiwire Array containing the arguments.
+ */
+JsRef
+hiwire_CallMethodId(JsRef obj, Js_Identifier* name, JsRef args);
+
+/**
+ * name is the method name, as a Js_Identifier
+ * Arguments are specified as a NULL-terminated variable arguments list of
+ * JsRefs.
+ */
+JsRef
+hiwire_CallMethodId_va(JsRef obj, Js_Identifier* name, ...);
+
+JsRef
+hiwire_CallMethodId_OneArg(JsRef obj, Js_Identifier* name, JsRef arg);
 
 /**
  * Calls the constructor of a class object.
@@ -306,68 +370,6 @@ hiwire_get_length(JsRef idobj);
 bool
 hiwire_get_bool(JsRef idobj);
 
-/**
- * Check whether `typeof obj.has === "function"`
- */
-bool
-hiwire_has_has_method(JsRef idobj);
-
-/**
- * Does `obj.has(val)`. Doesn't check type of return value, if it isn't a
- * boolean or an integer it will get coerced to false.
- */
-bool
-hiwire_call_has_method(JsRef idobj, JsRef idval);
-
-/**
- * Check whether `typeof obj.includes === "function"`.
- */
-bool
-hiwire_has_includes_method(JsRef idobj);
-
-/**
- * Does `obj.includes(val)`. Doesn't check type of return value, if it isn't a
- * boolean or an integer it will get coerced to `false`.
- */
-bool
-hiwire_call_includes_method(JsRef idobj, JsRef idval);
-
-/**
- * Check whether `typeof obj.get === "function"`.
- */
-bool
-hiwire_has_get_method(JsRef idobj);
-
-/**
- * Call `obj.get(key)`. If the result is `undefined`, we check for a `has`
- * method and if one is present call `obj.has(key)`. If this returns false we
- * return `NULL` to signal a `KeyError` otherwise we return `Js_Undefined`. If
- * no `has` method is present, we return `Js_Undefined`.
- */
-JsRef
-hiwire_call_get_method(JsRef idobj, JsRef idkey);
-
-/**
- * Check whether `typeof obj.set === "function"`.
- */
-bool
-hiwire_has_set_method(JsRef idobj);
-
-/**
- * Call `obj.set(key, value)`. Javascript standard is that `set` returns `false`
- * to indicate an error condition, but we ignore the return value.
- */
-errcode
-hiwire_call_set_method(JsRef idobj, JsRef idkey, JsRef idval);
-
-/**
- * Call `obj.delete(key)`. Javascript standard is that `delete` returns `false`
- * to indicate an error condition, if `false` is returned we return `-1` to
- * indicate the error.
- */
-errcode
-hiwire_call_delete_method(JsRef idobj, JsRef idkey);
-
 /**
  * Check whether the object is a PyProxy.
  */
diff --git a/src/core/jsproxy.c b/src/core/jsproxy.c
index 212c844fb..f1c263528 100644
--- a/src/core/jsproxy.c
+++ b/src/core/jsproxy.c
@@ -60,6 +60,13 @@ _Py_IDENTIFIER(set_exception);
 _Py_IDENTIFIER(set_result);
 _Py_IDENTIFIER(__await__);
 _Py_IDENTIFIER(__dir__);
+Js_IDENTIFIER(then);
+Js_IDENTIFIER(finally);
+Js_IDENTIFIER(has);
+Js_IDENTIFIER(get);
+Js_IDENTIFIER(set);
+Js_IDENTIFIER(delete);
+Js_IDENTIFIER(includes);
 
 static PyObject* asyncio_get_event_loop;
 static PyTypeObject* PyExc_BaseException_Type;
@@ -479,6 +486,25 @@ finally:
   return success ? 0 : -1;
 }
 
+// A helper method for jsproxy_subscript.
+EM_JS_REF(JsRef, JsProxy_subscript_js, (JsRef idobj, JsRef idkey), {
+  let obj = Module.hiwire.get_value(idobj);
+  let key = Module.hiwire.get_value(idkey);
+  let result = obj.get(key);
+  // clang-format off
+  if (result === undefined) {
+    // Try to distinguish between undefined and missing:
+    // If the object has a "has" method and it returns false for this key, the
+    // key is missing. Otherwise, assume key present and value was undefined.
+    // TODO: in absence of a "has" method, should we return None or KeyError?
+    if (obj.has && typeof obj.has === "function" && !obj.has(key)) {
+      return 0;
+    }
+  }
+  // clang-format on
+  return Module.hiwire.new_value(result);
+});
+
 /**
  * __getitem__ for JsProxies that have a "get" method. Translates proxy[key] to
  * obj.get(key). Controlled by HAS_GET
@@ -493,7 +519,7 @@ JsProxy_subscript(PyObject* o, PyObject* pyidx)
 
   ididx = python2js(pyidx);
   FAIL_IF_NULL(ididx);
-  idresult = hiwire_call_get_method(self->js, ididx);
+  idresult = JsProxy_subscript_js(self->js, ididx);
   if (idresult == NULL) {
     if (!PyErr_Occurred()) {
       PyErr_SetObject(PyExc_KeyError, pyidx);
@@ -522,9 +548,12 @@ JsProxy_ass_subscript(PyObject* o, PyObject* pyidx, PyObject* pyvalue)
   bool success = false;
   JsRef ididx = NULL;
   JsRef idvalue = NULL;
+  JsRef jsresult = NULL;
   ididx = python2js(pyidx);
   if (pyvalue == NULL) {
-    if (hiwire_call_delete_method(self->js, ididx)) {
+    jsresult = hiwire_CallMethodId_OneArg(self->js, &JsId_delete, ididx);
+    FAIL_IF_NULL(jsresult);
+    if (!hiwire_to_bool(jsresult)) {
       if (!PyErr_Occurred()) {
         PyErr_SetObject(PyExc_KeyError, pyidx);
       }
@@ -533,12 +562,15 @@ JsProxy_ass_subscript(PyObject* o, PyObject* pyidx, PyObject* pyvalue)
   } else {
     idvalue = python2js(pyvalue);
     FAIL_IF_NULL(idvalue);
-    FAIL_IF_MINUS_ONE(hiwire_call_set_method(self->js, ididx, idvalue));
+    jsresult =
+      hiwire_CallMethodId_va(self->js, &JsId_set, ididx, idvalue, NULL);
+    FAIL_IF_NULL(jsresult);
   }
   success = true;
 finally:
   hiwire_CLEAR(ididx);
   hiwire_CLEAR(idvalue);
+  hiwire_CLEAR(jsresult);
   return success ? 0 : -1;
 }
 
@@ -551,13 +583,17 @@ finally:
 static int
 JsProxy_includes(JsProxy* self, PyObject* obj)
 {
+  JsRef jsresult = NULL;
   int result = -1;
   JsRef jsobj = python2js(obj);
   FAIL_IF_NULL(jsobj);
-  result = hiwire_call_includes_method(self->js, jsobj);
+  jsresult = hiwire_CallMethodId_OneArg(self->js, &JsId_includes, jsobj);
+  FAIL_IF_NULL(jsresult);
+  result = hiwire_to_bool(jsresult);
 
 finally:
   hiwire_CLEAR(jsobj);
+  hiwire_CLEAR(jsresult);
   return result;
 }
 
@@ -569,13 +605,17 @@ finally:
 static int
 JsProxy_has(JsProxy* self, PyObject* obj)
 {
+  JsRef jsresult = NULL;
   int result = -1;
   JsRef jsobj = python2js(obj);
   FAIL_IF_NULL(jsobj);
-  result = hiwire_call_has_method(self->js, jsobj);
+  jsresult = hiwire_CallMethodId_OneArg(self->js, &JsId_has, jsobj);
+  FAIL_IF_NULL(jsresult);
+  result = hiwire_to_bool(jsresult);
 
 finally:
   hiwire_CLEAR(jsobj);
+  hiwire_CLEAR(jsresult);
   return result;
 }
 
@@ -727,7 +767,7 @@ JsProxy_Await(JsProxy* self)
   FAIL_IF_NULL(promise_id);
   promise_handles = create_promise_handles(set_result, set_exception);
   FAIL_IF_NULL(promise_handles);
-  promise_result = hiwire_call_member(promise_id, "then", promise_handles);
+  promise_result = hiwire_CallMethodId(promise_id, &JsId_then, promise_handles);
   FAIL_IF_NULL(promise_result);
   result = _PyObject_CallMethodId(fut, &PyId___await__, NULL);
 
@@ -776,7 +816,7 @@ JsProxy_then(JsProxy* self, PyObject* args, PyObject* kwds)
   FAIL_IF_NULL(promise_id);
   promise_handles = create_promise_handles(onfulfilled, onrejected);
   FAIL_IF_NULL(promise_handles);
-  result_promise = hiwire_call_member(promise_id, "then", promise_handles);
+  result_promise = hiwire_CallMethodId(promise_id, &JsId_then, promise_handles);
   if (result_promise == NULL) {
     Py_CLEAR(onfulfilled);
     Py_CLEAR(onrejected);
@@ -815,7 +855,7 @@ JsProxy_catch(JsProxy* self, PyObject* onrejected)
   // even if the promise resolves successfully.
   promise_handles = create_promise_handles(NULL, onrejected);
   FAIL_IF_NULL(promise_handles);
-  result_promise = hiwire_call_member(promise_id, "then", promise_handles);
+  result_promise = hiwire_CallMethodId(promise_id, &JsId_then, promise_handles);
   if (result_promise == NULL) {
     Py_DECREF(onrejected);
     FAIL();
@@ -856,7 +896,8 @@ JsProxy_finally(JsProxy* self, PyObject* onfinally)
   // `create_once_callable`.
   proxy = create_once_callable(onfinally);
   FAIL_IF_NULL(proxy);
-  result_promise = hiwire_call_member_va(promise_id, "finally", proxy, NULL);
+  result_promise =
+    hiwire_CallMethodId_va(promise_id, &JsId_finally, proxy, NULL);
   if (result_promise == NULL) {
     Py_DECREF(onfinally);
     FAIL();
@@ -1657,16 +1698,16 @@ JsProxy_create_with_this(JsRef object, JsRef this)
   if (hiwire_has_length(object)) {
     type_flags |= HAS_LENGTH;
   }
-  if (hiwire_has_get_method(object)) {
+  if (hiwire_HasMethodId(object, &JsId_get)) {
     type_flags |= HAS_GET;
   }
-  if (hiwire_has_set_method(object)) {
+  if (hiwire_HasMethodId(object, &JsId_set)) {
     type_flags |= HAS_SET;
   }
-  if (hiwire_has_has_method(object)) {
+  if (hiwire_HasMethodId(object, &JsId_has)) {
     type_flags |= HAS_HAS;
   }
-  if (hiwire_has_includes_method(object)) {
+  if (hiwire_HasMethodId(object, &JsId_includes)) {
     type_flags |= HAS_INCLUDES;
   }
   if (hiwire_is_typedarray(object)) {
diff --git a/src/core/pyproxy.c b/src/core/pyproxy.c
index a545aa5d2..13d6bdb7a 100644
--- a/src/core/pyproxy.c
+++ b/src/core/pyproxy.c
@@ -658,7 +658,7 @@ FutureDoneCallback_call_resolve(FutureDoneCallback* self, PyObject* result)
   JsRef result_js = NULL;
   JsRef output = NULL;
   result_js = python2js(result);
-  output = hiwire_call_va(self->resolve_handle, result_js, NULL);
+  output = hiwire_call_OneArg(self->resolve_handle, result_js);
 
   hiwire_CLEAR(result_js);
   hiwire_CLEAR(output);
@@ -678,7 +678,7 @@ FutureDoneCallback_call_reject(FutureDoneCallback* self)
   // wrap_exception looks up the current exception and wraps it in a Js error.
   excval = wrap_exception();
   FAIL_IF_NULL(excval);
-  result = hiwire_call_va(self->reject_handle, excval, NULL);
+  result = hiwire_call_OneArg(self->reject_handle, excval);
 
   success = true;
 finally: