diff --git a/toxcore/Messenger.c b/toxcore/Messenger.c
index 99281c73..8113a8f0 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -169,7 +169,7 @@ static int send_offline_packet(Messenger *m, int friendcon_id)
 }
 
 static int handle_status(void *object, int i, uint8_t status);
-static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len, void *userdata);
+static int handle_packet(void *object, int i, const uint8_t *temp, uint16_t len, void *userdata);
 static int handle_custom_lossy_packet(void *object, int friend_num, const uint8_t *packet, uint16_t length);
 
 static int32_t init_new_friend(Messenger *m, const uint8_t *real_pk, uint8_t status)
@@ -1622,7 +1622,7 @@ static void break_files(const Messenger *m, int32_t friendnumber)
 /* return -1 on failure, 0 on success.
  */
 static int handle_filecontrol(Messenger *m, int32_t friendnumber, uint8_t receive_send, uint8_t filenumber,
-                              uint8_t control_type, uint8_t *data, uint16_t length)
+                              uint8_t control_type, const uint8_t *data, uint16_t length)
 {
     if (receive_send > 1) {
         return -1;
@@ -2055,7 +2055,7 @@ static int handle_status(void *object, int i, uint8_t status)
     return 0;
 }
 
-static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len, void *userdata)
+static int handle_packet(void *object, int i, const uint8_t *temp, uint16_t len, void *userdata)
 {
     if (len == 0) {
         return -1;
@@ -2063,7 +2063,7 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len, void
 
     Messenger *m = object;
     uint8_t packet_id = temp[0];
-    uint8_t *data = temp + 1;
+    const uint8_t *data = temp + 1;
     uint32_t data_length = len - 1;
 
     if (m->friendlist[i].status != FRIEND_ONLINE) {
@@ -2295,7 +2295,7 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len, void
             real_filenumber += 1;
             real_filenumber <<= 16;
             uint16_t file_data_length = (data_length - 1);
-            uint8_t *file_data;
+            const uint8_t *file_data;
 
             if (file_data_length == 0) {
                 file_data = NULL;
diff --git a/toxcore/friend_connection.c b/toxcore/friend_connection.c
index 0779fb20..7c8471a0 100644
--- a/toxcore/friend_connection.c
+++ b/toxcore/friend_connection.c
@@ -392,7 +392,7 @@ static void dht_pk_callback(void *object, int32_t number, const uint8_t *dht_pub
     onion_set_friend_DHT_pubkey(fr_c->onion_c, friend_con->onion_friendnum, dht_public_key);
 }
 
-static int handle_packet(void *object, int number, uint8_t *data, uint16_t length, void *userdata)
+static int handle_packet(void *object, int number, const uint8_t *data, uint16_t length, void *userdata)
 {
     if (length == 0) {
         return -1;
@@ -647,7 +647,8 @@ void set_dht_temp_pk(Friend_Connections *fr_c, int friendcon_id, const uint8_t *
  * return -1 on failure
  */
 int friend_connection_callbacks(Friend_Connections *fr_c, int friendcon_id, unsigned int index,
-                                int (*status_callback)(void *object, int id, uint8_t status), int (*data_callback)(void *object, int id, uint8_t *data,
+                                int (*status_callback)(void *object, int id, uint8_t status), int (*data_callback)(void *object, int id,
+                                        const uint8_t *data,
                                         uint16_t length, void *userdata), int (*lossy_data_callback)(void *object, int id, const uint8_t *data,
                                                 uint16_t length), void *object,
                                 int number)
diff --git a/toxcore/friend_connection.h b/toxcore/friend_connection.h
index cbc6b9a1..a939b17c 100644
--- a/toxcore/friend_connection.h
+++ b/toxcore/friend_connection.h
@@ -83,7 +83,7 @@ typedef struct {
         void *status_callback_object;
         int status_callback_id;
 
-        int (*data_callback)(void *object, int id, uint8_t *data, uint16_t length, void *userdata);
+        int (*data_callback)(void *object, int id, const uint8_t *data, uint16_t length, void *userdata);
         void *data_callback_object;
         int data_callback_id;
 
@@ -158,7 +158,8 @@ int friend_add_tcp_relay(Friend_Connections *fr_c, int friendcon_id, IP_Port ip_
  * return -1 on failure
  */
 int friend_connection_callbacks(Friend_Connections *fr_c, int friendcon_id, unsigned int index,
-                                int (*status_callback)(void *object, int id, uint8_t status), int (*data_callback)(void *object, int id, uint8_t *data,
+                                int (*status_callback)(void *object, int id, uint8_t status), int (*data_callback)(void *object, int id,
+                                        const uint8_t *data,
                                         uint16_t length, void *userdata), int (*lossy_data_callback)(void *object, int id, const uint8_t *data,
                                                 uint16_t length), void *object,
                                 int number);
diff --git a/toxcore/net_crypto.c b/toxcore/net_crypto.c
index e2d7e494..940feb04 100644
--- a/toxcore/net_crypto.c
+++ b/toxcore/net_crypto.c
@@ -2142,7 +2142,7 @@ int connection_status_handler(const Net_Crypto *c, int crypt_connection_id,
  * return 0 on success.
  */
 int connection_data_handler(const Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
-                            int id, uint8_t *data, uint16_t length, void *userdata), void *object, int id)
+                            int id, const uint8_t *data, uint16_t length, void *userdata), void *object, int id)
 {
     Crypto_Connection *conn = get_crypto_connection(c, crypt_connection_id);
 
diff --git a/toxcore/net_crypto.h b/toxcore/net_crypto.h
index 6a3ba40f..52c6265e 100644
--- a/toxcore/net_crypto.h
+++ b/toxcore/net_crypto.h
@@ -135,7 +135,7 @@ typedef struct {
     void *connection_status_callback_object;
     int connection_status_callback_id;
 
-    int (*connection_data_callback)(void *object, int id, uint8_t *data, uint16_t length, void *userdata);
+    int (*connection_data_callback)(void *object, int id, const uint8_t *data, uint16_t length, void *userdata);
     void *connection_data_callback_object;
     int connection_data_callback_id;
 
@@ -275,7 +275,7 @@ int connection_status_handler(const Net_Crypto *c, int crypt_connection_id,
  * return 0 on success.
  */
 int connection_data_handler(const Net_Crypto *c, int crypt_connection_id, int (*connection_data_callback)(void *object,
-                            int id, uint8_t *data, uint16_t length, void *userdata), void *object, int id);
+                            int id, const uint8_t *data, uint16_t length, void *userdata), void *object, int id);
 
 
 /* Set function to be called when connection with crypt_connection_id receives a lossy data packet of length.