diff --git a/tools/debugger/kdd/kdd.c b/tools/debugger/kdd/kdd.c
index 3ebda9b12c..866532f0c7 100644
--- a/tools/debugger/kdd/kdd.c
+++ b/tools/debugger/kdd/kdd.c
@@ -79,11 +79,11 @@ typedef struct {
 /* State of the debugger stub */
 typedef struct {
     union {
-        uint8_t txb[sizeof (kdd_hdr) + 65536];   /* Marshalling area for tx */
+        uint8_t txb[sizeof (kdd_hdr)];           /* Marshalling area for tx */
         kdd_pkt txp;                 /* Also readable as a packet structure */
     };
     union {
-        uint8_t rxb[sizeof (kdd_hdr) + 65536];   /* Marshalling area for rx */
+        uint8_t rxb[sizeof (kdd_hdr)];           /* Marshalling area for rx */
         kdd_pkt rxp;                 /* Also readable as a packet structure */
     };
     unsigned int cur;       /* Offset into rx where we'll put the next byte */
diff --git a/tools/debugger/kdd/kdd.h b/tools/debugger/kdd/kdd.h
index bfb00ba5c5..b9a17440df 100644
--- a/tools/debugger/kdd/kdd.h
+++ b/tools/debugger/kdd/kdd.h
@@ -68,7 +68,6 @@ typedef struct {
     uint16_t len;     /* Payload length, excl. header and trailing byte */
     uint32_t id;      /* Echoed in responses */
     uint32_t sum;     /* Unsigned sum of all payload bytes */
-    uint8_t payload[0];
 } PACKED kdd_hdr;
 
 #define KDD_PKT_CMD 0x0002      /* Debugger commands (and replies to them) */
@@ -323,7 +322,7 @@ typedef struct {
         kdd_msg msg;
         kdd_reg reg;
         kdd_stc stc;
-        uint8_t payload[0];
+        uint8_t payload[65536];
     };
 } PACKED kdd_pkt;