diff --git a/cores/stm32l4/CDC.cpp b/cores/stm32l4/CDC.cpp
index aa5ee0bc..fbca22ee 100644
--- a/cores/stm32l4/CDC.cpp
+++ b/cores/stm32l4/CDC.cpp
@@ -72,10 +72,10 @@ CDC::CDC(struct _stm32l4_usbd_cdc_t *usbd_cdc, bool serialEvent)
 
 void CDC::begin(unsigned long baudrate)
 {
-    begin(baudrate, (uint8_t)SERIAL_8N1);
+    begin(baudrate, SERIAL_8N1);
 }
 
-void CDC::begin(unsigned long baudrate, uint16_t config)
+void CDC::begin(unsigned long baudrate, uint32_t config)
 {
     /* If USBD_CDC has already been enabled/initialized by STDIO, just add the notify.
      */
diff --git a/cores/stm32l4/HardwareSerial.h b/cores/stm32l4/HardwareSerial.h
index 655bc84b..7f8d35f2 100644
--- a/cores/stm32l4/HardwareSerial.h
+++ b/cores/stm32l4/HardwareSerial.h
@@ -57,7 +57,7 @@ class HardwareSerial : public Stream
 {
   public:
     virtual void begin(unsigned long);
-    virtual void begin(unsigned long baudrate, uint16_t config);
+    virtual void begin(unsigned long baudrate, uint32_t config);
     virtual void end();
     virtual int available(void) = 0;
     virtual int peek(void) = 0;
diff --git a/cores/stm32l4/USBAPI.h b/cores/stm32l4/USBAPI.h
index d4ccde73..479dc638 100644
--- a/cores/stm32l4/USBAPI.h
+++ b/cores/stm32l4/USBAPI.h
@@ -59,7 +59,7 @@ class CDC : public HardwareSerial
 public:
     CDC(struct _stm32l4_usbd_cdc_t *usbd_cdc, bool serialEvent);
     void begin(unsigned long baudRate);
-    void begin(unsigned long baudrate, uint16_t config);
+    void begin(unsigned long baudrate, uint32_t config);
     void end(void);
 
     int available(void);
diff --git a/cores/stm32l4/Uart.cpp b/cores/stm32l4/Uart.cpp
index 102caa69..c56c3284 100644
--- a/cores/stm32l4/Uart.cpp
+++ b/cores/stm32l4/Uart.cpp
@@ -61,7 +61,7 @@ void Uart::begin(unsigned long baudrate)
     begin(baudrate, SERIAL_8N1, &_rx_data[0], sizeof(_rx_data));
 }
 
-void Uart::begin(unsigned long baudrate, uint16_t config)
+void Uart::begin(unsigned long baudrate, uint32_t config)
 {
     begin(baudrate, config, &_rx_data[0], sizeof(_rx_data));
 }
@@ -71,7 +71,7 @@ void Uart::begin(unsigned long baudrate, uint8_t *buffer, size_t size)
     begin(baudrate, SERIAL_8N1, buffer, size);
 }
 
-void Uart::begin(unsigned long baudrate, uint16_t config, uint8_t *buffer, size_t size)
+void Uart::begin(unsigned long baudrate, uint32_t config, uint8_t *buffer, size_t size)
 {
     if (_uart->state != UART_STATE_INIT) {
 	flush();
diff --git a/cores/stm32l4/Uart.h b/cores/stm32l4/Uart.h
index 3a3bf42e..20ed7de0 100644
--- a/cores/stm32l4/Uart.h
+++ b/cores/stm32l4/Uart.h
@@ -38,9 +38,9 @@ class Uart : public HardwareSerial
 public:
     Uart(struct _stm32l4_uart_t *uart, unsigned int instance, const struct _stm32l4_uart_pins_t *pins, unsigned int priority, unsigned int mode, bool serialEvent);
     void begin(unsigned long baudRate);
-    void begin(unsigned long baudrate, uint16_t config);
+    void begin(unsigned long baudrate, uint32_t config);
     void begin(unsigned long baudRate, uint8_t *buffer, size_t size);
-    void begin(unsigned long baudrate, uint16_t config, uint8_t *buffer, size_t size);
+    void begin(unsigned long baudrate, uint32_t config, uint8_t *buffer, size_t size);
     void end();
     int available();
     int availableForWrite(void);