SoftwareSerial library won't compile on attiny85

I am trying to use the SoftwareSerial library on an ATtiny85 and when I try to compile the following code:

#include <SoftwareSerial.h>

void setup(){ }

void loop(){ }

I get the following errors:

/Applications/ error: conflicting return type specified for 'virtual size_t SoftwareSerial::write(uint8_t)'
/Users/oren/Documents/Arduino/hardware/tiny/cores/tiny/Print.h:71: error: overriding 'virtual void Print::write(uint8_t)'

It seems that the header file won't compile properly? Can anyone please provide any help??

Thank you!

You are using a core that does not properly support SoftwareSerial.
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