Nuclear level lifetimes have been measured in two superdeformed bands in Hg-194 using the Doppler-shift attenuation method. Average transition quadrupole moments derived from the life-times of an excited and yrast superdeformed bands are Q(t) = 17.6(30) and 17.2(20) eb, respectively. The Doppler shifts of the excited band relative to the yrast band indicate a slight difference in quadrupole moments [+4(5)%], assuming similar side feeding. These results imply that the second well is stable and rigid with respect to the particle excitation responsible for this excited band.