diff --git a/src/serial.rs b/src/serial.rs
index 7af493f4..569c18ca 100644
--- a/src/serial.rs
+++ b/src/serial.rs
@@ -298,6 +298,13 @@ cfg_if! {
     }
 }
 
+cfg_if! {
+    if #[cfg(feature="gpio-f373")] {
+        impl<Otype> TxPin<USART3> for gpiob::PB8<AF7<Otype>> {}
+        impl<Otype> RxPin<USART3> for gpiob::PB9<AF7<Otype>> {}
+    }
+}
+
 cfg_if! {
     if #[cfg(not(feature = "gpio-f373"))] {
         impl<Otype> TxPin<USART2> for gpioa::PA14<AF7<Otype>> {}