diff --git a/src/interface/windows.rs b/src/interface/windows.rs
index e0b6aec..f639af6 100644
--- a/src/interface/windows.rs
+++ b/src/interface/windows.rs
@@ -276,8 +276,8 @@ pub fn interfaces() -> Vec<Interface> {
                 ipv6: ipv6_vec,
                 ipv6_scope_ids: ipv6_scope_id_vec,
                 flags,
-                transmit_speed: Some(cur.TransmitLinkSpeed),
-                receive_speed: Some(cur.ReceiveLinkSpeed),
+                transmit_speed: sys::sanitize_u64(cur.TransmitLinkSpeed),
+                receive_speed: sys::sanitize_u64(cur.ReceiveLinkSpeed),
                 #[cfg(feature = "gateway")]
                 gateway: if default_gateway.mac_addr == MacAddr::zero() {
                     None
diff --git a/src/sys/windows.rs b/src/sys/windows.rs
index ce59cd3..ce80782 100644
--- a/src/sys/windows.rs
+++ b/src/sys/windows.rs
@@ -5,3 +5,13 @@ pub const IFF_BROADCAST: u32 = ws::IFF_BROADCAST;
 pub const IFF_LOOPBACK: u32 = ws::IFF_LOOPBACK;
 pub const IFF_POINTOPOINT: u32 = ws::IFF_POINTTOPOINT;
 pub const IFF_MULTICAST: u32 = ws::IFF_MULTICAST;
+
+/// Convert u64::MAX to None.
+/// Used for Windows APIs that return invalid max values.
+pub(crate) fn sanitize_u64(val: u64) -> Option<u64> {
+    if val == u64::MAX {
+        None
+    } else {
+        Some(val)
+    }
+}