You can use the
-s snaplen flag to specify the size of each packet.
-s 0 sets the default packet size to 65535 bytes, which increases how long it takes to process packets and decreases the amount of packet buffering, according to the man page. Though this might work here, it may not be appropriate in other cases as it can cause packets to be lost.
A better practice would be to set the
snaplen flag to the smallest value needed to capture what's needed. Another answer suggests 1500 bytes to see the whole packet and 160 bytes if you're only interested in the headers.
-s 0 may work here, for future use it would be a better idea to start with
-s 1500 and adjust as needed.
Note that taking larger snap-shots both increases the amount of time
it takes to process packets and, effectively, decreases the
amount of packet buffering. This may cause packets to be lost. You
should limit snaplen to the smallest number that will capture the
protocol information you're interested in. Setting snaplen to 0
sets it to the default of 65535, for backwards compatibility with
recent older versions of tcpdump.