  Context. The I(15.01 A)/I(16.78 A) emission line intensity ratio in Fe XVII
has been reported to deviate from its theoretical value in solar and stellar
X-ray spectra. This is attributed to opacity in the 15.01 A line, leading to a
reduction in its intensity, and was interpreted in terms of a geometry in which
the emitters and absorbers are spatially distinct. Aims. We study the I(15.01
A)/I(16.78 A) intensity ratio for the active cool dwarf EV Lac, in both flare
and quiescent spectra. Methods. The observations were obtained with the
Reflection Grating Spectrometer on the XMM-Newton satellite. The emission
measure distribution versus temperature reconstruction technique is used for
our analysis. Results. We find that the 15.01 A line exhibits a significant
enhancement in intensity over the optically thin value. To our knowledge, this
is the first time that such an enhancement has been detected on such a sound
statistical basis. We interpret this enhancement in terms of a geometry in
which the emitters and absorbers are not spatially distinct, and where the
geometry is such that resonant pumping of the upper level has a greater effect
on the observed line intensity than resonant absorption in the line-of-sight.
