MSI B75MA-E33 does see 2Gb of memory from 4Gb

My old m/b is dead (Gigabyte GA-H55M-S2). My 2 x mushkin Essentials 2Gb DDR3 1333MHz was working fine on that m/b. I decided to purchase replacement MSI B75MA-E33 + i3-3240. Specifications says that this memory is supported.
But BIOS see only 2Gb. I tr...