diff --git a/variants/STM32L4xx/L433C(B-C)(T-U)_L443CC(T-U)/variant_CYGNET.h b/variants/STM32L4xx/L433C(B-C)(T-U)_L443CC(T-U)/variant_CYGNET.h
index bc4ff379dd..2b64142628 100644
--- a/variants/STM32L4xx/L433C(B-C)(T-U)_L443CC(T-U)/variant_CYGNET.h
+++ b/variants/STM32L4xx/L433C(B-C)(T-U)_L443CC(T-U)/variant_CYGNET.h
@@ -153,6 +153,14 @@
   #define PIN_SERIAL_TX         PA9
 #endif
 
+// Default pin used for generic `Serial2` instance
+#ifndef PIN_SERIAL2_RX
+  #define PIN_SERIAL2_RX         PA3_ALT1
+#endif
+#ifndef PIN_SERIAL2_TX
+  #define PIN_SERIAL2_TX         PA2_ALT1
+#endif
+
 // LPUART1
 #ifndef PIN_SERIAL_LP1_RX
   #define PIN_SERIAL_LP1_RX     PB10
diff --git a/variants/STM32L4xx/L4R5Z(G-I)Y_L4R9Z(G-I)Y_L4S5ZIY_L4S9ZIY/variant_SWAN_R5.h b/variants/STM32L4xx/L4R5Z(G-I)Y_L4R9Z(G-I)Y_L4S5ZIY_L4S9ZIY/variant_SWAN_R5.h
index c4c5b2de0b..01f0144f33 100644
--- a/variants/STM32L4xx/L4R5Z(G-I)Y_L4R9Z(G-I)Y_L4S5ZIY_L4S9ZIY/variant_SWAN_R5.h
+++ b/variants/STM32L4xx/L4R5Z(G-I)Y_L4R9Z(G-I)Y_L4S5ZIY_L4S9ZIY/variant_SWAN_R5.h
@@ -236,6 +236,14 @@
   #define PIN_SERIAL_TX         PA9
 #endif
 
+// Default pin used for generic 'Serial3' instance
+#ifndef PIN_SERIAL3_RX
+  #define PIN_SERIAL3_RX        PC5
+#endif
+#ifndef PIN_SERIAL3_TX
+  #define PIN_SERIAL3_TX        PC4
+#endif
+
 // LPUART1
 #ifndef PIN_SERIAL_LP1_RX
   #define PIN_SERIAL_LP1_RX     PG8