diff --git a/firmware/src/cardio.c b/firmware/src/cardio.c
index 75782d7..2b2d3cd 100644
--- a/firmware/src/cardio.c
+++ b/firmware/src/cardio.c
@@ -4,6 +4,7 @@
  */
 
 #include <stdlib.h>
+#include <stdio.h>
 #include <stdint.h>
 #include <stdbool.h>
 
diff --git a/firmware/src/usb_descriptors.c b/firmware/src/usb_descriptors.c
index 2019bf5..5f42958 100644
--- a/firmware/src/usb_descriptors.c
+++ b/firmware/src/usb_descriptors.c
@@ -23,6 +23,8 @@
  *
  */
 
+#include <stdio.h>
+
 #include "usb_descriptors.h"
 #include "pico/unique_id.h"
 #include "tusb.h"