The present invention relates to an annular barrier to be expanded in an annulus between a well tubular structure and an inside wall of a borehole downhole for providing zone isolation between a first zone and a second zone of the borehole, the annular barrier comprising a tubular metal part for mounting as part of the well tubular structure, an expandable sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face facing the inside wall of the borehole, each end of the expandable sleeve being connected with the tubular metal part, and an annular space between the inner face of the expandable sleeve and the tubular metal part, wherein the tubular part and the inner face of the expandable sleeve substantially hermetically enclose the annular space, the annular space comprising a compound adapted to expand the annular space, and wherein the expandable sleeve comprises two first sections abutting the ends of the expandable sleeve and a second section between the first sections, the first section of the expandable sleeve has a first inner diameter in an unexpanded condition of the annular barrier, and the second section of the expandable sleeve has a second inner diameter in the unexpanded condition, which second inner diameter is larger than the first inner diameter in the unexpanded condition, or the first sections have a first thickness which is larger than a second thickness of the second section in the unexpanded condition. Furthermore, the invention relates to a downhole system and a method of expanding an annular barrier.