diff --git a/cpu/sam0_common/periph/uart.c b/cpu/sam0_common/periph/uart.c
index cfd8cc93a2..dc8fb6a224 100644
--- a/cpu/sam0_common/periph/uart.c
+++ b/cpu/sam0_common/periph/uart.c
@@ -38,8 +38,13 @@
 
 /* default to fractional baud rate calculation */
 #if !defined(CONFIG_SAM0_UART_BAUD_FRAC) && defined(SERCOM_USART_BAUD_FRAC_BAUD)
+/* SAML21 has no fractional baud rate on SERCOM5 */
+#if defined(CPU_SAML21)
+#define CONFIG_SAM0_UART_BAUD_FRAC  0
+#else
 #define CONFIG_SAM0_UART_BAUD_FRAC  1
 #endif
+#endif
 
 /* SAMD20 defines no generic macro */
 #ifdef SERCOM_USART_CTRLA_TXPO_PAD0