diff --git a/converter/adb_usb/matrix.c b/converter/adb_usb/matrix.c
index a616d10e4..ee17f655f 100644
--- a/converter/adb_usb/matrix.c
+++ b/converter/adb_usb/matrix.c
@@ -100,9 +100,7 @@ uint8_t matrix_scan(void)
     } else if (codes == 0xFFFF) {   // power key release
         register_key(0xFF);
     } else if (key0 == 0xFF) {      // error
-        if (debug_matrix) print("adb_host_kbd_recv: ERROR(matrix cleared.)\n");
-        // clear matrix to unregister all keys
-        for (uint8_t i=0; i < MATRIX_ROWS; i++) matrix[i] = 0x00;
+        xprintf("adb_host_kbd_recv: ERROR(%02X)\n", codes);
         return key1;
     } else {
         register_key(key0);
diff --git a/protocol/adb.c b/protocol/adb.c
index 2baad3234..e4e26b7d7 100644
--- a/protocol/adb.c
+++ b/protocol/adb.c
@@ -40,6 +40,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include "adb.h"
+#include "debug.h"
 
 
 static inline void data_lo(void);
@@ -93,6 +94,7 @@ uint16_t adb_host_kbd_recv(void)
     }
     if (!read_bit()) {          // Startbit(1)
         // Service Request
+        dprintf("Startbit ERROR\n");
         return -2;
     }
 
@@ -104,6 +106,7 @@ uint16_t adb_host_kbd_recv(void)
     sei();
 
     if (stop) {
+        dprintf("Stopbit ERROR\n");
         return -3;
     }
     return data;