diff --git a/armsrc/cmd.c b/armsrc/cmd.c
index c179ed2a9..f2b432d33 100644
--- a/armsrc/cmd.c
+++ b/armsrc/cmd.c
@@ -26,7 +26,7 @@ bool g_reply_with_crc_on_fpc = true;
 bool g_reply_via_fpc = false;
 bool g_reply_via_usb = false;
 
-int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
+int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, const void *data, size_t len) {
     PacketResponseOLD txcmd = {CMD_UNKNOWN, {0, 0, 0}, {{0}}};
 
 //    for (size_t i = 0; i < sizeof(PacketResponseOLD); i++)
@@ -42,7 +42,7 @@ int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *d
     if (data && len) {
         len = MIN(len, PM3_CMD_DATA_SIZE);
         for (size_t i = 0; i < len; i++) {
-            txcmd.d.asBytes[i] = ((uint8_t *)data)[i];
+            txcmd.d.asBytes[i] = ((const uint8_t *)data)[i];
         }
     }
 
@@ -135,7 +135,7 @@ int reply_ng(uint16_t cmd, int16_t status, const uint8_t *data, size_t len) {
     return reply_ng_internal(cmd, status, data, len, true);
 }
 
-int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len) {
+int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, const void *data, size_t len) {
     int16_t status = PM3_SUCCESS;
     uint64_t arg[3] = {arg0, arg1, arg2};
     if (len > PM3_CMD_DATA_SIZE - sizeof(arg)) {
diff --git a/armsrc/cmd.h b/armsrc/cmd.h
index b578db8e8..22a79ce16 100644
--- a/armsrc/cmd.h
+++ b/armsrc/cmd.h
@@ -27,9 +27,9 @@ extern bool g_reply_with_crc_on_fpc;
 extern bool g_reply_via_fpc;
 extern bool g_reply_via_usb;
 
-int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int reply_old(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, const void *data, size_t len);
 int reply_ng(uint16_t cmd, int16_t status, const uint8_t *data, size_t len);
-int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, void *data, size_t len);
+int reply_mix(uint64_t cmd, uint64_t arg0, uint64_t arg1, uint64_t arg2, const void *data, size_t len);
 int receive_ng(PacketCommandNG *rx);
 
 #endif // _PROXMARK_CMD_H_