We examined six exoplanet host stars with non-standard Hipparcos astrometric solution , which may be indicative of unrecognised orbital motion . Using Hipparcos intermediate astrometric data , we detected the astrometric orbit of HD 5388 at a significance level of 99.4 % ( 2.7 \sigma ) . HD 5388 is a metal-deficient star and hosts a planet candidate with a minimum mass of 1.96 M _ { \mathrm { J } } discovered in 2010 . We determined its orbit inclination to be i = 178.3 ^ { +0.4 \circ } _ { -0.7 } and the corresponding mass of its companion HD~5388~b to be M _ { 2 } = 69 \pm 20 M _ { \mathrm { J } } . The orbit is seen almost face-on and the companion mass lies at the upper end of the brown-dwarf mass range . A mass lower than 13 M _ { \mathrm { J } } was excluded at the 3 \sigma -level . The astrometric motions of the five other stars had been investigated by other authors revealing two planetary companions , one stellar companion , and two statistically insignificant orbits . We conclude that HD 5388 b is not a planet but most likely a brown-dwarf companion . In addition , we find that the inclinations of the stellar rotation axis and the companion ’ s orbital axis differ significantly .