diff --git a/cpu/stm32_common/periph/uart.c b/cpu/stm32_common/periph/uart.c
index db3e7c9711..4f79f6a87d 100644
--- a/cpu/stm32_common/periph/uart.c
+++ b/cpu/stm32_common/periph/uart.c
@@ -112,7 +112,7 @@ static inline void uart_init_pins(uart_t uart, uart_rx_cb_t rx_cb)
 #endif
     /* configure RX pin */
     if (rx_cb) {
-        gpio_init(uart_config[uart].rx_pin, GPIO_IN);
+        gpio_init(uart_config[uart].rx_pin, GPIO_IN_PU);
 #ifndef CPU_FAM_STM32F1
         gpio_init_af(uart_config[uart].rx_pin, uart_config[uart].rx_af);
 #endif