  We analyze in detail supersymmetry breaking by compactification of the fifth
dimension in M-theory in the compactification pattern $11d \to 5d \to 4d$ and
find that a superpotential is generated for the complex fields coming from $5d$
hypermultiplets, namely the dilaton $S$ and the complex structure moduli. Using
general arguments it is shown that these fields are always stabilized such that
they don't contribute to supersymmetry breaking, which is completely saturated
by the K\"ahler moduli coming from vector multiplets.
  It is shown that this mechanism is the strong-coupling analog of the
Rohm-Witten quantization of the antisymmetric tensor field strength of string
theories. The effect of a gaugino condensate on one of the boundaries is also
considered.
