diff --git a/ipv4/helper_unix.go b/ipv4/helper_unix.go
index 4eab775..3a2df84 100644
--- a/ipv4/helper_unix.go
+++ b/ipv4/helper_unix.go
@@ -39,8 +39,8 @@
 	cv := reflect.ValueOf(c)
 	switch ce := cv.Elem(); ce.Kind() {
 	case reflect.Struct:
-		nfd := ce.FieldByName("conn").FieldByName("fd")
-		switch fe := nfd.Elem(); fe.Kind() {
+		netfd := ce.FieldByName("conn").FieldByName("fd")
+		switch fe := netfd.Elem(); fe.Kind() {
 		case reflect.Struct:
 			fd := fe.FieldByName("sysfd")
 			return int(fd.Int()), nil
diff --git a/ipv4/helper_windows.go b/ipv4/helper_windows.go
index 0733e3e..6de55f8 100644
--- a/ipv4/helper_windows.go
+++ b/ipv4/helper_windows.go
@@ -38,11 +38,11 @@
 	cv := reflect.ValueOf(c)
 	switch ce := cv.Elem(); ce.Kind() {
 	case reflect.Struct:
-		fd := ce.FieldByName("conn").FieldByName("fd")
-		switch fe := fd.Elem(); fe.Kind() {
+		netfd := ce.FieldByName("conn").FieldByName("fd")
+		switch fe := netfd.Elem(); fe.Kind() {
 		case reflect.Struct:
-			sysfd := fe.FieldByName("sysfd")
-			return syscall.Handle(sysfd.Uint()), nil
+			fd := fe.FieldByName("sysfd")
+			return syscall.Handle(fd.Uint()), nil
 		}
 	}
 	return syscall.InvalidHandle, errInvalidConnType