MSSFIX rule in IPTables

When enabling the log dropped packet feature, MTU fix errors also popup.

Mon Aug 21 16:45:50 2017 kern.warn kernel: [56033.675569] MSSFIX(wan): IN=wlan1-1 OUT=eth1.2 MAC=00:blabla00 SRC= DST=52blabla14 LEN=60 TOS=0x00 PREC=0x00 TTL=63 ID=41623 DF PROTO=TCP SPT=53004 DPT=443 WINDOW=14600 RES=0x00 SYN URGP=0

Ive traced it back to a mangle rule:

tcp flags:0x06/0x02 limit: avg 1000/sec burst 5 /* !fw3: wan (mtu_fix logging) */ LOG flags 0 level 4 prefix "MSSFIX(wan): "

How do I remove this but keep the dropped notices? Cant find the definition in /etc/.. or /etc/config/..