diff --git a/toxcore/Messenger.c b/toxcore/Messenger.c
index a3295170..954b31dd 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -1314,17 +1314,17 @@ int file_data(Messenger *m, int friendnumber, uint8_t filenumber, uint8_t *data,
 uint64_t file_dataremaining(Messenger *m, int friendnumber, uint8_t filenumber, uint8_t send_receive)
 {
     if (friend_not_valid(m, friendnumber))
-        return -1;
+        return 0;
 
     if (send_receive == 0) {
         if (m->friendlist[friendnumber].file_sending[filenumber].status == FILESTATUS_NONE)
-            return -1;
+            return 0;
 
         return m->friendlist[friendnumber].file_sending[filenumber].size -
                m->friendlist[friendnumber].file_sending[filenumber].transferred;
     } else {
         if (m->friendlist[friendnumber].file_receiving[filenumber].status == FILESTATUS_NONE)
-            return -1;
+            return 0;
 
         return m->friendlist[friendnumber].file_receiving[filenumber].size -
                m->friendlist[friendnumber].file_receiving[filenumber].transferred;
diff --git a/toxcore/tox.c b/toxcore/tox.c
index 02137b3c..f4e65ec8 100644
--- a/toxcore/tox.c
+++ b/toxcore/tox.c
@@ -620,7 +620,7 @@ int tox_filedata_size(Tox *tox, int friendnumber)
  *  send_receive is 0 if we want the sending files, 1 if we want the receiving.
  *
  *  return number of bytes remaining to be sent/received on success
- *  return -1 on failure
+ *  return 0 on failure
  */
 uint64_t tox_file_dataremaining(Tox *tox, int friendnumber, uint8_t filenumber, uint8_t send_receive)
 {
diff --git a/toxcore/tox.h b/toxcore/tox.h
index 735d991a..ea373488 100644
--- a/toxcore/tox.h
+++ b/toxcore/tox.h
@@ -544,7 +544,7 @@ int tox_filedata_size(Tox *tox, int friendnumber);
  *  send_receive is 0 if we want the sending files, 1 if we want the receiving.
  *
  *  return number of bytes remaining to be sent/received on success
- *  return -1 on failure
+ *  return 0 on failure
  */
 uint64_t tox_file_dataremaining(Tox *tox, int friendnumber, uint8_t filenumber, uint8_t send_receive);