diff --git a/bin/pt-diskstats b/bin/pt-diskstats
index 37c4d2d2..0bf2b23e 100755
--- a/bin/pt-diskstats
+++ b/bin/pt-diskstats
@@ -1550,8 +1550,11 @@ use List::Util qw( max first );
 
 use ReadKeyMini qw( GetTerminalSize );
 
-my (undef, $max_lines)    = GetTerminalSize();
-$Diskstats::printed_lines = $max_lines;
+my $max_lines;
+BEGIN {
+   (undef, $max_lines)       = GetTerminalSize();
+   $Diskstats::printed_lines = $max_lines;
+}
 
 my $diskstat_colno_for;
 BEGIN {
@@ -2399,6 +2402,9 @@ sub print_deltas {
 
    my @stats = $self->_calc_deltas();
 
+   $Diskstats::printed_lines = $max_lines
+      unless defined $Diskstats::printed_lines;
+
    if ( $self->{space_samples} && @stats && @stats > 1
          && !$Diskstats::last_was_header ) {
       print "\n";
diff --git a/lib/Diskstats.pm b/lib/Diskstats.pm
index 53cd12a4..13b49b6c 100644
--- a/lib/Diskstats.pm
+++ b/lib/Diskstats.pm
@@ -34,8 +34,11 @@ use List::Util qw( max first );
 
 use ReadKeyMini qw( GetTerminalSize );
 
-my (undef, $max_lines)    = GetTerminalSize();
-$Diskstats::printed_lines = $max_lines;
+my $max_lines;
+BEGIN {
+   (undef, $max_lines)       = GetTerminalSize();
+   $Diskstats::printed_lines = $max_lines;
+}
 
 my $diskstat_colno_for;
 BEGIN {
@@ -975,6 +978,9 @@ sub print_deltas {
 
    my @stats = $self->_calc_deltas();
 
+   $Diskstats::printed_lines = $max_lines
+      unless defined $Diskstats::printed_lines;
+
    if ( $self->{space_samples} && @stats && @stats > 1
          && !$Diskstats::last_was_header ) {
       # Print an empty line before the rows if we have more