diff --git a/tools/tools/ministat/ministat.c b/tools/tools/ministat/ministat.c
index 4b7c6a0e77fb..b8ca72a4bd8f 100644
--- a/tools/tools/ministat/ministat.c
+++ b/tools/tools/ministat/ministat.c
@@ -328,6 +328,8 @@ PlotSet(struct dataset *ds, int val)
 	int i, j, m, x;
 
 	pl = &plot;
+	if (pl->span == 0)
+		return;
 	m = 1;
 	i = -1;
 	j = 0;
@@ -380,6 +382,10 @@ DumpPlot(void)
 	int i, j, k;
 
 	pl = &plot;
+	if (pl->span == 0) {
+		printf("[no plot, span is zero width]\n");
+		return;
+	}
 
 	putchar('+');
 	for (i = 0; i < pl->width; i++)
diff --git a/usr.bin/ministat/ministat.c b/usr.bin/ministat/ministat.c
index 4b7c6a0e77fb..b8ca72a4bd8f 100644
--- a/usr.bin/ministat/ministat.c
+++ b/usr.bin/ministat/ministat.c
@@ -328,6 +328,8 @@ PlotSet(struct dataset *ds, int val)
 	int i, j, m, x;
 
 	pl = &plot;
+	if (pl->span == 0)
+		return;
 	m = 1;
 	i = -1;
 	j = 0;
@@ -380,6 +382,10 @@ DumpPlot(void)
 	int i, j, k;
 
 	pl = &plot;
+	if (pl->span == 0) {
+		printf("[no plot, span is zero width]\n");
+		return;
+	}
 
 	putchar('+');
 	for (i = 0; i < pl->width; i++)