gcc cross-compile -mips1 not generating MIPS-I

I'm am targeting an old router need MIPS-I executables but -mips1 produces MIPS32 executables.

Here is the compile command:

buildroot-2019.02.5/output/host/bin/mips-linux-gcc-7.4.0 -march=mips1 -mtune=mips1 -static ~/helloworld.c -o /tmp/hw.1013  -msoft-float

But the file is MIPS32, not MIPS-I

file /tmp/hw.1013

/tmp/hw.1013: ELF 32-bit MSB executable, MIPS, MIPS32 version 1 (SYSV), statically linked, not stripped

Older versions of gcc produce the correct MIPS-I binaries.

./mips-gcc --version
uClibc mips-rawgcc (GCC) 4.1.2

./mips-gcc -march=mips1  -static ~/helloworld.c -o /tmp/hw.1013  -msoft-float 
file /tmp/hw.1013
/tmp/hw.1013: ELF 32-bit MSB executable, MIPS, MIPS-I version 1 (SYSV), statically linked, not stripped