diff --git a/board-support/raspberrypi-rp2040/src/hal/usb.zig b/board-support/raspberrypi-rp2040/src/hal/usb.zig
index 31770470..575a4d3c 100644
--- a/board-support/raspberrypi-rp2040/src/hal/usb.zig
+++ b/board-support/raspberrypi-rp2040/src/hal/usb.zig
@@ -42,7 +42,6 @@ pub const utf8ToUtf16Le = usb.utf8Toutf16Le;
 
 pub var EP0_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.EP0_OUT_ADDR,
         .attributes = @intFromEnum(usb.TransferType.Control),
@@ -57,7 +56,6 @@ pub var EP0_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP0_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.EP0_IN_ADDR,
         .attributes = @intFromEnum(usb.TransferType.Control),
diff --git a/core/src/core/usb.zig b/core/src/core/usb.zig
index a7b4e564..12d7cfb5 100644
--- a/core/src/core/usb.zig
+++ b/core/src/core/usb.zig
@@ -513,7 +513,7 @@ pub const Dir = enum(u8) {
 /// Describes an endpoint within an interface
 pub const EndpointDescriptor = extern struct {
     /// Length of this struct, must be 7.
-    length: u8,
+    length: u8 = 7,
     /// Type of this descriptor, must be `Endpoint`.
     descriptor_type: DescType,
     /// Address of this endpoint, where the bottom 4 bits give the endpoint
@@ -530,7 +530,7 @@ pub const EndpointDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [7]u8 {
         var out: [7]u8 = undefined;
-        out[0] = 7; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.endpoint_address;
         out[3] = self.attributes;
@@ -544,7 +544,7 @@ pub const EndpointDescriptor = extern struct {
 /// Description of an interface within a configuration.
 pub const InterfaceDescriptor = extern struct {
     /// Length of this structure, must be 9.
-    length: u8,
+    length: u8 = 9,
     /// Type of this descriptor, must be `Interface`.
     descriptor_type: DescType,
     /// ID of this interface.
@@ -566,7 +566,7 @@ pub const InterfaceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.interface_number;
         out[3] = self.alternate_setting;
@@ -582,7 +582,7 @@ pub const InterfaceDescriptor = extern struct {
 /// Description of a single available device configuration.
 pub const ConfigurationDescriptor = extern struct {
     /// Length of this structure, must be 9.
-    length: u8,
+    length: u8 = 9,
     /// Type of this descriptor, must be `Config`.
     descriptor_type: DescType,
     /// Total length of all descriptors in this configuration, concatenated.
@@ -610,7 +610,7 @@ pub const ConfigurationDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.total_length & 0xff);
         out[3] = @intCast((self.total_length >> 8) & 0xff);
@@ -627,7 +627,7 @@ pub const ConfigurationDescriptor = extern struct {
 /// typically the first thing the host asks for.
 pub const DeviceDescriptor = extern struct {
     /// Length of this structure, must be 18.
-    length: u8,
+    length: u8 = 18,
     /// Type of this descriptor, must be `Device`.
     descriptor_type: DescType,
     /// Version of the device descriptor / USB protocol, in binary-coded
@@ -658,7 +658,7 @@ pub const DeviceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [18]u8 {
         var out: [18]u8 = undefined;
-        out[0] = 18; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_usb & 0xff);
         out[3] = @intCast((self.bcd_usb >> 8) & 0xff);
@@ -705,7 +705,7 @@ pub const DeviceQualifierDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [10]u8 {
         var out: [10]u8 = undefined;
-        out[0] = 10; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_usb & 0xff);
         out[3] = @intCast((self.bcd_usb >> 8) & 0xff);
diff --git a/core/src/core/usb/hid.zig b/core/src/core/usb/hid.zig
index c63e28ae..16308638 100644
--- a/core/src/core/usb/hid.zig
+++ b/core/src/core/usb/hid.zig
@@ -103,7 +103,7 @@ pub const HidDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = self.length;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_hid & 0xff);
         out[3] = @intCast((self.bcd_hid >> 8) & 0xff);
diff --git a/examples/raspberrypi-rp2040/src/usb_device.zig b/examples/raspberrypi-rp2040/src/usb_device.zig
index 8f2d74e4..50b790db 100644
--- a/examples/raspberrypi-rp2040/src/usb_device.zig
+++ b/examples/raspberrypi-rp2040/src/usb_device.zig
@@ -38,7 +38,6 @@ fn ep1_out_callback(dc: *usb.DeviceConfiguration, data: []const u8) void {
 // add your own endpoints to...
 pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.Out.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Bulk),
@@ -55,7 +54,6 @@ pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.In.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Bulk),
@@ -73,7 +71,6 @@ pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
 // This is our device configuration
 pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     .device_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.DeviceDescriptor))),
         .descriptor_type = usb.DescType.Device,
         .bcd_usb = 0x0110,
         .device_class = 0,
@@ -89,7 +86,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .num_configurations = 1,
     },
     .interface_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.InterfaceDescriptor))),
         .descriptor_type = usb.DescType.Interface,
         .interface_number = 0,
         .alternate_setting = 0,
@@ -101,7 +97,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .interface_s = 0,
     },
     .config_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor))),
         .descriptor_type = usb.DescType.Config,
         .total_length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor) + @sizeOf(usb.InterfaceDescriptor) + @sizeOf(usb.EndpointDescriptor) + @sizeOf(usb.EndpointDescriptor))),
         .num_interfaces = 1,
diff --git a/examples/raspberrypi-rp2040/src/usb_hid.zig b/examples/raspberrypi-rp2040/src/usb_hid.zig
index 752111ad..7f7677a7 100644
--- a/examples/raspberrypi-rp2040/src/usb_hid.zig
+++ b/examples/raspberrypi-rp2040/src/usb_hid.zig
@@ -38,7 +38,6 @@ fn ep1_out_callback(dc: *usb.DeviceConfiguration, data: []const u8) void {
 // add your own endpoints to...
 pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.Out.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Interrupt),
@@ -55,7 +54,6 @@ pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.In.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Interrupt),
@@ -73,7 +71,6 @@ pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
 // This is our device configuration
 pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     .device_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.DeviceDescriptor))),
         .descriptor_type = usb.DescType.Device,
         .bcd_usb = 0x0200,
         .device_class = 0,
@@ -91,7 +88,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .num_configurations = 1,
     },
     .interface_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.InterfaceDescriptor))),
         .descriptor_type = usb.DescType.Interface,
         .interface_number = 0,
         .alternate_setting = 0,
@@ -103,7 +99,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .interface_s = 0,
     },
     .config_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor))),
         .descriptor_type = usb.DescType.Config,
         .total_length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor) + @sizeOf(usb.InterfaceDescriptor) + @sizeOf(usb.EndpointDescriptor) + @sizeOf(usb.EndpointDescriptor))),
         .num_interfaces = 1,