diff --git a/src/browser/dom/document.zig b/src/browser/dom/document.zig
index ea3c8e76..fe4a499a 100644
--- a/src/browser/dom/document.zig
+++ b/src/browser/dom/document.zig
@@ -129,7 +129,7 @@ pub const Document = struct {
     pub fn _createElement(self: *parser.Document, tag_name: []const u8, page: *Page) !CreateElementResult {
         const custom_element = page.window.custom_elements._get(tag_name) orelse {
             const e = try parser.documentCreateElement(self, tag_name);
-            return .{.element = try Element.toInterface(e)};
+            return .{ .element = try Element.toInterface(e) };
         };
 
         var result: Env.Function.Result = undefined;
@@ -142,7 +142,7 @@ pub const Document = struct {
             });
             return err;
         };
-        return .{.custom = js_obj};
+        return .{ .custom = js_obj };
     }
 
     pub fn _createElementNS(self: *parser.Document, ns: []const u8, tag_name: []const u8) !ElementUnion {
diff --git a/src/browser/html/elements.zig b/src/browser/html/elements.zig
index 350c51cc..1bb5b5fa 100644
--- a/src/browser/html/elements.zig
+++ b/src/browser/html/elements.zig
@@ -115,13 +115,7 @@ pub const HTMLElement = struct {
     pub const subtype = .node;
 
     pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
-        const constructor_name = try js_this.constructorName(page.call_arena);
-        const tag_name = page.window.custom_elements.names.get(constructor_name) orelse {
-            return error.IllegalContructor;
-        };
-
-        const el = try parser.documentCreateElement(@ptrCast(page.window.document), tag_name);
-        return el;
+        return constructHtmlElement(page, js_this);
     }
 
     pub fn get_style(e: *parser.ElementHTML, page: *Page) !*CSSStyleDeclaration {
@@ -186,6 +180,10 @@ pub const HTMLMediaElement = struct {
     pub const Self = parser.MediaElement;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 // HTML elements
@@ -195,6 +193,10 @@ pub const HTMLUnknownElement = struct {
     pub const Self = parser.Unknown;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 // https://html.spec.whatwg.org/#the-a-element
@@ -203,6 +205,10 @@ pub const HTMLAnchorElement = struct {
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
 
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
+
     pub fn get_target(self: *parser.Anchor) ![]const u8 {
         return try parser.anchorGetTarget(self);
     }
@@ -440,144 +446,240 @@ pub const HTMLAppletElement = struct {
     pub const Self = parser.Applet;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLAreaElement = struct {
     pub const Self = parser.Area;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLAudioElement = struct {
     pub const Self = parser.Audio;
     pub const prototype = *HTMLMediaElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLBRElement = struct {
     pub const Self = parser.BR;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLBaseElement = struct {
     pub const Self = parser.Base;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLBodyElement = struct {
     pub const Self = parser.Body;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLButtonElement = struct {
     pub const Self = parser.Button;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLCanvasElement = struct {
     pub const Self = parser.Canvas;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDListElement = struct {
     pub const Self = parser.DList;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDataElement = struct {
     pub const Self = parser.Data;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDataListElement = struct {
     pub const Self = parser.DataList;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDialogElement = struct {
     pub const Self = parser.Dialog;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDirectoryElement = struct {
     pub const Self = parser.Directory;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLDivElement = struct {
     pub const Self = parser.Div;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLEmbedElement = struct {
     pub const Self = parser.Embed;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLFieldSetElement = struct {
     pub const Self = parser.FieldSet;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLFontElement = struct {
     pub const Self = parser.Font;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLFrameElement = struct {
     pub const Self = parser.Frame;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLFrameSetElement = struct {
     pub const Self = parser.FrameSet;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLHRElement = struct {
     pub const Self = parser.HR;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLHeadElement = struct {
     pub const Self = parser.Head;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLHeadingElement = struct {
     pub const Self = parser.Heading;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLHtmlElement = struct {
     pub const Self = parser.Html;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLIFrameElement = struct {
     pub const Self = parser.IFrame;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLImageElement = struct {
@@ -585,6 +687,10 @@ pub const HTMLImageElement = struct {
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
 
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
+
     pub fn get_alt(self: *parser.Image) ![]const u8 {
         return try parser.imageGetAlt(self);
     }
@@ -644,6 +750,10 @@ pub const HTMLInputElement = struct {
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
 
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
+
     pub fn get_defaultValue(self: *parser.Input) ![]const u8 {
         return try parser.inputGetDefaultValue(self);
     }
@@ -732,114 +842,190 @@ pub const HTMLLIElement = struct {
     pub const Self = parser.LI;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLLabelElement = struct {
     pub const Self = parser.Label;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLLegendElement = struct {
     pub const Self = parser.Legend;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLLinkElement = struct {
     pub const Self = parser.Link;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLMapElement = struct {
     pub const Self = parser.Map;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLMetaElement = struct {
     pub const Self = parser.Meta;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLMeterElement = struct {
     pub const Self = parser.Meter;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLModElement = struct {
     pub const Self = parser.Mod;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLOListElement = struct {
     pub const Self = parser.OList;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLObjectElement = struct {
     pub const Self = parser.Object;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLOptGroupElement = struct {
     pub const Self = parser.OptGroup;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLOptionElement = struct {
     pub const Self = parser.Option;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLOutputElement = struct {
     pub const Self = parser.Output;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLParagraphElement = struct {
     pub const Self = parser.Paragraph;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLParamElement = struct {
     pub const Self = parser.Param;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLPictureElement = struct {
     pub const Self = parser.Picture;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLPreElement = struct {
     pub const Self = parser.Pre;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLProgressElement = struct {
     pub const Self = parser.Progress;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLQuoteElement = struct {
     pub const Self = parser.Quote;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 // https://html.spec.whatwg.org/#the-script-element
@@ -848,6 +1034,10 @@ pub const HTMLScriptElement = struct {
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
 
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
+
     pub fn get_src(self: *parser.Script) !?[]const u8 {
         return try parser.elementGetAttribute(
             parser.scriptToElt(self),
@@ -982,96 +1172,160 @@ pub const HTMLSourceElement = struct {
     pub const Self = parser.Source;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLSpanElement = struct {
     pub const Self = parser.Span;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLStyleElement = struct {
     pub const Self = parser.Style;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableElement = struct {
     pub const Self = parser.Table;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableCaptionElement = struct {
     pub const Self = parser.TableCaption;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableCellElement = struct {
     pub const Self = parser.TableCell;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableColElement = struct {
     pub const Self = parser.TableCol;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableRowElement = struct {
     pub const Self = parser.TableRow;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTableSectionElement = struct {
     pub const Self = parser.TableSection;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTemplateElement = struct {
     pub const Self = parser.Template;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTextAreaElement = struct {
     pub const Self = parser.TextArea;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTimeElement = struct {
     pub const Self = parser.Time;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTitleElement = struct {
     pub const Self = parser.Title;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLTrackElement = struct {
     pub const Self = parser.Track;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLUListElement = struct {
     pub const Self = parser.UList;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub const HTMLVideoElement = struct {
     pub const Self = parser.Video;
     pub const prototype = *HTMLElement;
     pub const subtype = .node;
+
+    pub fn constructor(page: *Page, js_this: Env.JsThis) !*parser.Element {
+        return constructHtmlElement(page, js_this);
+    }
 };
 
 pub fn toInterface(comptime T: type, e: *parser.Element) !T {
@@ -1149,6 +1403,17 @@ pub fn toInterface(comptime T: type, e: *parser.Element) !T {
     };
 }
 
+fn constructHtmlElement(page: *Page, js_this: Env.JsThis) !*parser.Element {
+    const constructor_name = try js_this.constructorName(page.call_arena);
+    std.debug.print("constructor: {s}\n", .{constructor_name});
+    if (!page.window.custom_elements.lookup.contains(constructor_name)) {
+        return error.IllegalContructor;
+    }
+
+    const el = try parser.documentCreateElement(@ptrCast(page.window.document), constructor_name);
+    return el;
+}
+
 const testing = @import("../../testing.zig");
 test "Browser.HTML.Element" {
     var runner = try testing.jsRunner(testing.tracking_allocator, .{});
diff --git a/src/browser/webcomponents/custom_element_registry.zig b/src/browser/webcomponents/custom_element_registry.zig
index 66abe0f6..3e429a67 100644
--- a/src/browser/webcomponents/custom_element_registry.zig
+++ b/src/browser/webcomponents/custom_element_registry.zig
@@ -26,10 +26,6 @@ const Page = @import("../page.zig").Page;
 const Element = @import("../dom/element.zig").Element;
 
 pub const CustomElementRegistry = struct {
-    // JS FunctionName -> Definition Name, so that, given a function, we can
-    // create the element with the right tag
-    names: std.StringHashMapUnmanaged([]const u8) = .empty,
-
     // tag_name -> Function
     lookup: std.StringHashMapUnmanaged(Env.Function) = .empty,
 
@@ -37,18 +33,14 @@ pub const CustomElementRegistry = struct {
         log.info(.browser, "define custom element", .{ .name = tag_name });
 
         const arena = page.arena;
-
         const gop = try self.lookup.getOrPut(arena, tag_name);
-        if (gop.found_existing) {
-            return error.DuplicateCustomElement;
+        if (!gop.found_existing) {
+            errdefer _ = self.lookup.remove(tag_name);
+            const owned_tag_name = try arena.dupe(u8, tag_name);
+            gop.key_ptr.* = owned_tag_name;
         }
-        errdefer _ = self.lookup.remove(tag_name);
-
-        const owned_tag_name = try arena.dupe(u8, tag_name);
-        gop.key_ptr.* = owned_tag_name;
         gop.value_ptr.* = fun;
-
-        try self.names.putNoClobber(arena, try fun.getName(arena), owned_tag_name);
+        fun.setName(tag_name);
     }
 
     pub fn _get(self: *CustomElementRegistry, name: []const u8) ?Env.Function {
diff --git a/src/runtime/js.zig b/src/runtime/js.zig
index 76a5ee0a..5f6e95b4 100644
--- a/src/runtime/js.zig
+++ b/src/runtime/js.zig
@@ -1262,6 +1262,11 @@ pub fn Env(comptime State: type, comptime WebApis: type) type {
                 return valueToString(allocator, name, self.js_context.isolate, self.js_context.v8_context);
             }
 
+            pub fn setName(self: *const Function, name: []const u8) void {
+                const v8_name = v8.String.initUtf8(self.js_context.isolate, name);
+                self.func.castToFunction().setName(v8_name);
+            }
+
             pub fn withThis(self: *const Function, value: anytype) !Function {
                 const this_obj = if (@TypeOf(value) == JsObject)
                     value.js_obj