You are correct. I updated the core file as stated and it compiles successfully, but now the com port is acting squirrely when I try to upload code:
Sketch uses 7456 bytes (26%) of program storage space. Maximum is 28672 bytes.
Global variables use 612 bytes (23%) of dynamic memory, leaving 1948 bytes for local variables. Maximum is 2560 bytes.
avrdude: ser_open(): can't set com-state for "\.\COM4"
Failed uploading: uploading error: exit status 1