diff --git a/src/gui/components/Button.zig b/src/gui/components/Button.zig
index 9f60f18c6f..12b415e489 100644
--- a/src/gui/components/Button.zig
+++ b/src/gui/components/Button.zig
@@ -54,6 +54,7 @@ pub var buttonUniforms: struct {
 
 pos: Vec2f,
 size: Vec2f,
+disabled: bool = false,
 pressed: bool = false,
 hovered: bool = false,
 onAction: gui.Callback,
@@ -127,20 +128,22 @@ pub fn mainButtonPressed(self: *Button, _: Vec2f) void {
 pub fn mainButtonReleased(self: *Button, mousePosition: Vec2f) void {
 	if(self.pressed) {
 		self.pressed = false;
-		if(GuiComponent.contains(self.pos, self.size, mousePosition)) {
+		if(!self.disabled and GuiComponent.contains(self.pos, self.size, mousePosition)) {
 			self.onAction.run();
 		}
 	}
 }
 
 pub fn render(self: *Button, mousePosition: Vec2f) void {
-	const textures = if(self.pressed)
+	const textures = if(self.disabled)
+		normalTextures
+	else if(self.pressed)
 		pressedTextures
 	else if(GuiComponent.contains(self.pos, self.size, mousePosition) and self.hovered)
 		hoveredTextures
 	else
 		normalTextures;
-	draw.setColor(0xff000000);
+	draw.setColor(if(self.disabled) 0xa0000000 else 0xff000000);
 	textures.texture.bindTo(0);
 	pipeline.bind(draw.getScissor());
 	self.hovered = false;
@@ -151,7 +154,7 @@ pub fn render(self: *Button, mousePosition: Vec2f) void {
 		const lowerTexture = (textures.outlineTextureSize - Vec2f{1, 1})/Vec2f{2, 2}/textures.outlineTextureSize;
 		const upperTexture = (textures.outlineTextureSize + Vec2f{1, 1})/Vec2f{2, 2}/textures.outlineTextureSize;
 		textures.outlineTexture.bindTo(0);
-		draw.setColor(0xffffffff);
+		draw.setColor(if(self.disabled) 0xffa0a0a0 else 0xffffffff);
 		// Corners:
 		graphics.draw.boundSubImage(self.pos + Vec2f{0, 0}, cornerSize, .{0, 0}, cornerSizeUV);
 		graphics.draw.boundSubImage(self.pos + Vec2f{self.size[0], 0} - Vec2f{cornerSize[0], 0}, cornerSize, .{upperTexture[0], 0}, cornerSizeUV);
diff --git a/src/gui/windows/multiplayer.zig b/src/gui/windows/multiplayer.zig
index c60a5751c1..7a9aac4374 100644
--- a/src/gui/windows/multiplayer.zig
+++ b/src/gui/windows/multiplayer.zig
@@ -19,6 +19,7 @@ pub var window = GuiWindow{
 
 var ipAddressLabel: *Label = undefined;
 var ipAddressEntry: *TextInput = undefined;
+var joinButton: *Button = undefined;
 
 const padding: f32 = 8;
 
@@ -85,6 +86,24 @@ fn copyIp(_: usize) void {
 	main.Window.setClipboardString(ipAddress);
 }
 
+fn isValidAddress(str: []const u8) bool {
+	// min doamin name length is 2
+	if(str.len < 2) return false;
+
+	// check if port is valid
+	var iter = std.mem.splitScalar(u8, str, ':');
+	const address = iter.first();
+	const portPart = iter.rest();
+	if(str.len > address.len) {
+		if(portPart.len == 0) return false;
+
+		const port = if(portPart[0] == '?') portPart[1..] else portPart;
+		_ = std.fmt.parseUnsigned(u16, port, 10) catch return false;
+	}
+
+	return std.net.isValidHostName(address);
+}
+
 pub fn onOpen() void {
 	const list = VerticalList.init(.{padding, 16 + padding}, 300, 16);
 	list.add(Label.init(.{0, 0}, width, "Please send your IP to the host of the game and enter the host's IP below.", .center));
@@ -94,7 +113,8 @@ pub fn onOpen() void {
 	list.add(Button.initText(.{0, 0}, 100, "Copy IP", .{.callback = &copyIp}));
 	ipAddressEntry = TextInput.init(.{0, 0}, width, 32, settings.lastUsedIPAddress, .{.callback = &join}, .{});
 	list.add(ipAddressEntry);
-	list.add(Button.initText(.{0, 0}, 100, "Join", .{.callback = &join}));
+	joinButton = Button.initText(.{0, 0}, 100, "Join", .{.callback = &join});
+	list.add(joinButton);
 	list.finish(.center);
 	window.rootComponent = list.toComponent();
 	window.contentSize = window.rootComponent.?.pos() + window.rootComponent.?.size() + @as(Vec2f, @splat(padding));
@@ -131,4 +151,6 @@ pub fn update() void {
 		gotIpAddress.store(false, .monotonic);
 		ipAddressLabel.updateText(ipAddress);
 	}
+
+	joinButton.disabled = !isValidAddress(ipAddressEntry.currentString.items);
 }