        if (pt.bias > d_bias) {
            pt.bias -= d_bias;
            uint256 d_slope = changes_weight[_gauge_addr][t];
-           pt.slope -= d_slope;
+           if(pt.slope >= d.slope) {
+               pt.slope -= d_slope;
+           } else {
+               pt.slope = 0;
+           }
        } else {
            pt.bias = 0;
            pt.slope = 0;
        }
