diff --git a/scripts/bootgraph.pl b/scripts/bootgraph.pl
index 4baf4998558..479fb4ea891 100644
--- a/scripts/bootgraph.pl
+++ b/scripts/bootgraph.pl
@@ -46,7 +46,7 @@ my %pids;
 
 while (<>) {
 	my $line = $_;
-	if ($line =~ /([0-9\.]+)\] calling  ([a-zA-Z\_]+)\+/) {
+	if ($line =~ /([0-9\.]+)\] calling  ([a-zA-Z0-9\_]+)\+/) {
 		my $func = $2;
 		if ($done == 0) {
 			$start{$func} = $1;
@@ -60,7 +60,7 @@ while (<>) {
 		$count = $count + 1;
 	}
 
-	if ($line =~ /([0-9\.]+)\] initcall ([a-zA-Z\_]+)\+.*returned/) {
+	if ($line =~ /([0-9\.]+)\] initcall ([a-zA-Z0-9\_]+)\+.*returned/) {
 		if ($done == 0) {
 			$end{$2} = $1;
 			$maxtime = $1;
@@ -75,8 +75,8 @@ while (<>) {
 }
 
 if ($count == 0) {
-	print "No data found in the dmesg. Make sure CONFIG_PRINTK_TIME is enabled and\n";
-	print "that initcall_debug is passed on the kernel command line.\n\n";
+	print "No data found in the dmesg. Make sure that 'printk.time=1' and\n";
+	print "'initcall_debug' are passed on the kernel command line.\n\n";
 	print "Usage: \n";
 	print "      dmesg | perl scripts/bootgraph.pl > output.svg\n\n";
 	exit;