diff --git a/src/fs/otp.c b/src/fs/otp.c
index f0d930b..0c07ca6 100644
--- a/src/fs/otp.c
+++ b/src/fs/otp.c
@@ -15,6 +15,7 @@
  * along with this program. If not, see <https://www.gnu.org/licenses/>.
  */
 
+ #include <stdio.h>
 #include "picokeys.h"
 #include "otp.h"