A computer-implemented method for referencing a mutable out-of-line monitor for a shared object in read-only memory, comprising creating a lockword with a pointer field set to zero and a pre-set inflated bit when the object is stored in read-only memory. An out-of-line monitor table is referenced when encountering the lockword with the pointer field set to zero and the pre-set inflated bit. The desired monitor referenced in the out-of-line monitor table is identified based on the address of the lockword.