[en] A quadratic dispersion relation is derived for ion temperature gradient driven modes in toroidal geometry without any expansion in inverse aspect ratio and including the effect of dissipative trapped electrons. It is shown that for finite trapping the η_i-mode stability thresholds are discontinously shifted compared to the case without trapping. Furthermore the thresholds are not sensitive to the magnitude of the trapping. A stability requirement on the density scale length L_n which has to be larger than about half the major radius R and an upper and a lower η_i stability threshold which grow linearly with ±2L_n/R are derived. (orig.)