diff --git a/cpu/stm32l1/periph/gpio.c b/cpu/stm32l1/periph/gpio.c
index 77fd05d5c91bf..9de5baea76e8a 100644
--- a/cpu/stm32l1/periph/gpio.c
+++ b/cpu/stm32l1/periph/gpio.c
@@ -79,7 +79,7 @@ int gpio_init(gpio_t pin, gpio_mode_t mode)
     port->PUPDR |=  (((mode >> 2) & 0x3) << (2 * pin_num));
     /* set output mode */
     port->OTYPER &= ~(1 << pin_num);
-    port->OTYPER &=  (((mode >> 4) & 0x1) << (2 * pin_num));
+    port->OTYPER |=  (((mode >> 4) & 0x1) << pin_num);
     /* finally set pin speed to maximum and reset output */
     port->OSPEEDR |= (3 << (2 * pin_num));
     port->BRR = (1 << pin_num);