diff --git a/sys/src/cmd/acme/cols.c b/sys/src/cmd/acme/cols.c
index a5e0fbd28..f66634d57 100644
--- a/sys/src/cmd/acme/cols.c
+++ b/sys/src/cmd/acme/cols.c
@@ -197,8 +197,11 @@ colresize(Column *c, Rectangle r)
 		w->maxlines = 0;
 		if(i == c->nw-1)
 			r1.max.y = r.max.y;
-		else
-			r1.max.y = r1.min.y+(Dy(w->r)+Border)*Dy(r)/Dy(c->r);
+		else {
+			r1.max.y = r1.min.y;
+			if(Dy(c->r) != 0)
+				r1.max.y += (Dy(w->r)+Border)*Dy(r)/Dy(c->r);
+		}
 		r2 = r1;
 		r2.max.y = r2.min.y+Border;
 		draw(screen, r2, display->black, nil, ZP);