OVM 2.1.1 code not compilable using Questasim 6.4b

Hi,

when I compile the ovm-2.1.1 code using Questasim 6.4b, getting the following error. Please anybody help me in this.

** Error: ../ovm-2.1.1/src/base/base.svh(25): near “const”: syntax error, unexpected “const”, expecting ‘;’ or ‘,’

** Error: C:/questasim_6.4c/win32/vlog failed.

README-QUESTA.txt says 6.4d or later is required. 6.4 is from 2008. 6.6 is current.