diff --git a/src/frontend/plotting/plotcurv.c b/src/frontend/plotting/plotcurv.c
index ce11525c9..2c274923a 100644
--- a/src/frontend/plotting/plotcurv.c
+++ b/src/frontend/plotting/plotcurv.c
@@ -137,6 +137,17 @@ ft_graf(struct dvec *v, struct dvec *xs, bool nostart)
                 realpart(xs->v_compdata[i]);
             dy = isreal(v) ? v->v_realdata[i] :
                 realpart(v->v_compdata[i]);
+			/* check for NAN */
+			if (isnan(dy)) {
+				lx = dx;
+				ly = dy;
+				continue;
+			}
+			else if (!isnan(dy) && isnan(ly)) {
+				lx = dx;
+				ly = dy;
+			}
+			/* end of check */
             if ((i == 0 || (dir > 0 ? lx > dx : dir < 0 ? lx < dx : 0)) &&
                 (mono || (xs->v_plot && xs->v_plot->pl_scale == xs)))
             {