diff --git a/drivers/include/periph/adc.h b/drivers/include/periph/adc.h
index d4e6458b3e..16105c355d 100644
--- a/drivers/include/periph/adc.h
+++ b/drivers/include/periph/adc.h
@@ -56,6 +56,7 @@
 #define PERIPH_ADC_H
 
 #include <limits.h>
+#include <stdint.h>
 
 #include "periph_cpu.h"
 #include "periph_conf.h"
@@ -125,7 +126,7 @@ int adc_init(adc_t line);
  * @return                  the sampled value on success
  * @return                  -1 if resolution is not applicable
  */
-int adc_sample(adc_t line, adc_res_t res);
+int32_t adc_sample(adc_t line, adc_res_t res);
 
 #ifdef __cplusplus
 }