For the first time, we have performed 10-μm high spatial resolution imaging of Galactic globular clusters (GGCs) with ESO-TIMMI, and have obtained a firm detection in a 35x35 arcsec^2 field of omega Centauri, about 70 arcsec south and 10 arcsec east of the cluster centre. The detected object is in good positional coincidence with the IRAS point source 13237-4713 and with the Mira variable V42. The most plausible explanation for the detected emission is the presence of a circumstellar envelope around the red giant as a consequence of a currently occurring mass-loss event. This dusty structure, the tracer of a warm dust component, is not resolved within the instrumental point spread function, in good agreement with an expected equilibrium radius of only a few hundred stellar radii. In addition, the coincidence between the Mira variable and the IRAS point source is interesting, because it seems to be a rare event in a globular cluster and implies that most of the mass-loss episode is actually occurring within a short time-scale, in agreement with the theory of mass loss driven by thermal pulsation even in low-mass stars.