diff --git a/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp b/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
index dac3bcb776..5e314a8674 100644
--- a/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
+++ b/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
@@ -741,7 +741,7 @@ static @fully_qualified_name@* impl_from(JS::VM& vm, JS::GlobalObject& global_ob
         auto scoped_generator = generator.fork();
         scoped_generator.set("return_type", return_type.name);
 
-        if (return_type.name == "void") {
+        if (return_type.name == "undefined") {
             scoped_generator.append(R"~~~(
     return JS::js_undefined();
 )~~~");
@@ -918,7 +918,7 @@ JS_DEFINE_NATIVE_FUNCTION(@wrapper_class@::@function.name:snakecase@)
 
         function_generator.set(".arguments", arguments_builder.string_view());
 
-        if (function.return_type.name != "void") {
+        if (function.return_type.name != "undefined") {
             function_generator.append(R"~~~(
     auto retval = impl->@function.name:snakecase@(@.arguments@);
 )~~~");
diff --git a/Libraries/LibWeb/DOM/Element.idl b/Libraries/LibWeb/DOM/Element.idl
index fe5c462a48..386b44db3a 100644
--- a/Libraries/LibWeb/DOM/Element.idl
+++ b/Libraries/LibWeb/DOM/Element.idl
@@ -3,7 +3,7 @@ interface Element : Node {
     readonly attribute DOMString tagName;
 
     DOMString? getAttribute(DOMString qualifiedName);
-    void setAttribute(DOMString qualifiedName, DOMString value);
+    undefined setAttribute(DOMString qualifiedName, DOMString value);
 
     readonly attribute Element? firstElementChild;
     readonly attribute Element? lastElementChild;
diff --git a/Libraries/LibWeb/DOM/Event.idl b/Libraries/LibWeb/DOM/Event.idl
index 51d50b2c53..a577092cae 100644
--- a/Libraries/LibWeb/DOM/Event.idl
+++ b/Libraries/LibWeb/DOM/Event.idl
@@ -7,14 +7,14 @@ interface Event {
 
     readonly attribute unsigned short eventPhase;
 
-    void stopPropagation();
+    undefined stopPropagation();
     attribute boolean cancelBubble;
-    void stopImmediatePropagation();
+    undefined stopImmediatePropagation();
 
     readonly attribute boolean bubbles;
     readonly attribute boolean cancelable;
     attribute boolean returnValue;
-    void preventDefault();
+    undefined preventDefault();
     readonly attribute boolean defaultPrevented;
     readonly attribute boolean composed;
 
diff --git a/Libraries/LibWeb/DOM/EventTarget.idl b/Libraries/LibWeb/DOM/EventTarget.idl
index 140fa4f39a..2dacfae0e2 100644
--- a/Libraries/LibWeb/DOM/EventTarget.idl
+++ b/Libraries/LibWeb/DOM/EventTarget.idl
@@ -1,6 +1,6 @@
 interface EventTarget {
 
-    void addEventListener(DOMString type, EventListener? callback);
-    void removeEventListener(DOMString type, EventListener? callback);
+    undefined addEventListener(DOMString type, EventListener? callback);
+    undefined removeEventListener(DOMString type, EventListener? callback);
 
 };
diff --git a/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl b/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
index a86dcaf76b..bcfa544c67 100644
--- a/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
+++ b/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl
@@ -1,28 +1,28 @@
 interface CanvasRenderingContext2D {
 
-    void fillRect(double x, double y, double w, double h);
-    void strokeRect(double x, double y, double w, double h);
+    undefined fillRect(double x, double y, double w, double h);
+    undefined strokeRect(double x, double y, double w, double h);
 
-    void scale(double x, double y);
-    void translate(double x, double y);
-    void rotate(double radians);
+    undefined scale(double x, double y);
+    undefined translate(double x, double y);
+    undefined rotate(double radians);
 
-    void beginPath();
-    void closePath();
-    void fill(DOMString fillRule);
-    void stroke();
-    void moveTo(double x, double y);
-    void lineTo(double x, double y);
-    void quadraticCurveTo(double cpx, double cpy, double x, double y);
+    undefined beginPath();
+    undefined closePath();
+    undefined fill(DOMString fillRule);
+    undefined stroke();
+    undefined moveTo(double x, double y);
+    undefined lineTo(double x, double y);
+    undefined quadraticCurveTo(double cpx, double cpy, double x, double y);
 
-    void drawImage(HTMLImageElement image, double dx, double dy);
+    undefined drawImage(HTMLImageElement image, double dx, double dy);
 
     attribute DOMString fillStyle;
     attribute DOMString strokeStyle;
     attribute double lineWidth;
 
     ImageData createImageData(double sw, double sh);
-    void putImageData(ImageData imagedata, double dx, double dy);
+    undefined putImageData(ImageData imagedata, double dx, double dy);
 
     readonly attribute HTMLCanvasElement canvas;
 
diff --git a/Libraries/LibWeb/HTML/HTMLFormElement.idl b/Libraries/LibWeb/HTML/HTMLFormElement.idl
index fd32600233..81d4fe37f4 100644
--- a/Libraries/LibWeb/HTML/HTMLFormElement.idl
+++ b/Libraries/LibWeb/HTML/HTMLFormElement.idl
@@ -5,6 +5,6 @@ interface HTMLFormElement : HTMLElement {
     [Reflect=accept-charset] attribute DOMString acceptCharset;
     [Reflect=novalidate] attribute boolean noValidate;
 
-    void submit();
+    undefined submit();
 
 };