diff --git a/enumerator/enumerator.go b/enumerator/enumerator.go
index 41f88fe..552330e 100644
--- a/enumerator/enumerator.go
+++ b/enumerator/enumerator.go
@@ -6,7 +6,7 @@
 
 package enumerator
 
-//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output syscall_windows.go usb_windows.go
+//go:generate go run golang.org/x/sys/windows/mkwinsyscall -output syscall_windows.go usb_windows.go
 
 // PortDetails contains detailed information about USB serial port.
 // Use GetDetailedPortsList function to retrieve it.
diff --git a/enumerator/syscall_windows.go b/enumerator/syscall_windows.go
index d969274..1dbcd9c 100644
--- a/enumerator/syscall_windows.go
+++ b/enumerator/syscall_windows.go
@@ -1,4 +1,4 @@
-// MACHINE GENERATED BY 'go generate' COMMAND; DO NOT EDIT
+// Code generated by 'go generate'; DO NOT EDIT.
 
 package enumerator
 
@@ -11,6 +11,31 @@ import (
 
 var _ unsafe.Pointer
 
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return nil
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
 var (
 	modsetupapi = windows.NewLazySystemDLL("setupapi.dll")
 
@@ -36,7 +61,7 @@ func _setupDiClassGuidsFromNameInternal(class *uint16, guid *guid, guidSize uint
 	r1, _, e1 := syscall.Syscall6(procSetupDiClassGuidsFromNameW.Addr(), 4, uintptr(unsafe.Pointer(class)), uintptr(unsafe.Pointer(guid)), uintptr(guidSize), uintptr(unsafe.Pointer(requiredSize)), 0, 0)
 	if r1 == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
@@ -49,7 +74,7 @@ func setupDiGetClassDevs(guid *guid, enumerator *string, hwndParent uintptr, fla
 	set = devicesSet(r0)
 	if set == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
@@ -61,7 +86,7 @@ func setupDiDestroyDeviceInfoList(set devicesSet) (err error) {
 	r1, _, e1 := syscall.Syscall(procSetupDiDestroyDeviceInfoList.Addr(), 1, uintptr(set), 0, 0)
 	if r1 == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
@@ -73,7 +98,7 @@ func setupDiEnumDeviceInfo(set devicesSet, index uint32, info *devInfoData) (err
 	r1, _, e1 := syscall.Syscall(procSetupDiEnumDeviceInfo.Addr(), 3, uintptr(set), uintptr(index), uintptr(unsafe.Pointer(info)))
 	if r1 == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
@@ -85,7 +110,7 @@ func setupDiGetDeviceInstanceId(set devicesSet, devInfo *devInfoData, devInstanc
 	r1, _, e1 := syscall.Syscall6(procSetupDiGetDeviceInstanceIdW.Addr(), 5, uintptr(set), uintptr(unsafe.Pointer(devInfo)), uintptr(devInstanceId), uintptr(devInstanceIdSize), uintptr(unsafe.Pointer(requiredSize)), 0)
 	if r1 == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
@@ -98,7 +123,7 @@ func setupDiOpenDevRegKey(set devicesSet, devInfo *devInfoData, scope dicsScope,
 	hkey = syscall.Handle(r0)
 	if hkey == 0 {
 		if e1 != 0 {
-			err = error(e1)
+			err = errnoErr(e1)
 		} else {
 			err = syscall.EINVAL
 		}
diff --git a/zsyscall_windows.go b/zsyscall_windows.go
index f6005ea..9c42379 100644
--- a/zsyscall_windows.go
+++ b/zsyscall_windows.go
@@ -1,4 +1,4 @@
-// MACHINE GENERATED BY 'go generate' COMMAND; DO NOT EDIT
+// Code generated by 'go generate'; DO NOT EDIT.
 
 package serial