diff --git a/cpu/fe310/periph/uart.c b/cpu/fe310/periph/uart.c
index 3bf54c58c7..80b3907774 100644
--- a/cpu/fe310/periph/uart.c
+++ b/cpu/fe310/periph/uart.c
@@ -41,7 +41,9 @@ static inline void _uart_isr(uart_t dev)
 
     /* Intr cleared automatically when data is read */
     while ((data & UART_RXFIFO_EMPTY) != (uint32_t)UART_RXFIFO_EMPTY) {
-        isr_ctx[dev].rx_cb(isr_ctx[dev].arg, (uint8_t)(data & 0xff));
+        if (isr_ctx[dev].rx_cb) {
+            isr_ctx[dev].rx_cb(isr_ctx[dev].arg, (uint8_t)(data & 0xff));
+        }
         data = _REG32(uart_config[dev].addr, UART_REG_RXFIFO);
     }
 }
@@ -60,6 +62,16 @@ void uart_isr(int num)
     }
 }
 
+static void _drain(uart_t dev)
+{
+    uint32_t data = _REG32(uart_config[dev].addr, UART_REG_RXFIFO);
+
+    /* Intr cleared automatically when data is read */
+    while ((data & UART_RXFIFO_EMPTY) != (uint32_t)UART_RXFIFO_EMPTY) {
+        data = _REG32(uart_config[dev].addr, UART_REG_RXFIFO);
+    }
+}
+
 int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
 {
     uint32_t uartDiv;
@@ -107,6 +119,11 @@ int uart_init(uart_t dev, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
         set_external_isr_cb(uart_config[dev].isr_num, uart_isr);
         PLIC_enable_interrupt(uart_config[dev].isr_num);
         PLIC_set_priority(uart_config[dev].isr_num, UART_ISR_PRIO);
+
+        /* avoid trap by emptying RX FIFO */
+        _drain(dev);
+
+        /* enable RX interrupt */
         _REG32(uart_config[dev].addr, UART_REG_IE) = UART_IP_RXWM;
 
         /* Enable RX */