I had the same problem, but found out that the dump file was actually a MSSQL Server backup, not MySQL.
Sometimes legacy backup files play tricks on us. Check your dump file.
On terminal window:
~$ cat mybackup.dmp
The result was:
TAPE??G?"5,^}???Microsoft SQL ServerSPAD^LSFMB8..... etc...
To stop processing the cat command:
CTRL + C