diff --git a/scripts/bootgraph.pl b/scripts/bootgraph.pl
index 479fb4ea8914e3db0146f74b2ce6fccf384d2366..5e7316e5aa395a4c5da260c1d2890336b4c70039 100644
--- a/scripts/bootgraph.pl
+++ b/scripts/bootgraph.pl
@@ -110,6 +110,12 @@ while (($key,$value) = each %start) {
 
 	if ($duration >= $threshold) {
 		my $s, $s2, $e, $y;
+		$pid = $pids{$key};
+
+		if (!defined($rows{$pid})) {
+			$rows{$pid} = $rowscount;
+			$rowscount = $rowscount + 1;
+		}
 		$s = ($value - $firsttime) * $mult;
 		$s2 = $s + 6;
 		$e = ($end{$key} - $firsttime) * $mult;