  In this Letter we discuss a modification to the criterion for the common
envelope (CE) event to result in envelope dispersion. We emphasize that the
current energy criterion for the CE phase is not sufficient for an instability
of the CE, nor for an ejection. However, in some cases, stellar envelopes
undergo stationary mass outflows, which are likely to occur during the slow
spiral-in stage of the CE event. We propose the condition for such outflows, in
a manner similar to the currently standard $\alpha_{\rm
CE}\lambda$-prescription but with an addition of $P/\rho$ term in the energy
balance equation, accounting therefore for the enthalpy of the envelope rather
than merely the gas internal energy. This produces a significant correction,
which might help to dispense with an unphysically high value of energy
efficiency parameter during CE phase, currently required in the binary
population synthesis studies to make the production of low-mass X-ray binaries
(LMXBs) with a black hole companion to match the observations.
