--- check_memory.orig	2015-08-18 18:17:21.000000000 +0200
+++ check_memory.new	2015-11-29 15:14:07.493644046 +0100
@@ -104,12 +104,23 @@
   or $np->nagios_exit('CRITICAL', "Could not run $FREECMD");
 
 warn("Output from $FREECMD:\n") if ($verbose > 1);
-my ($used, $free);
+my $new_format = 0;
+my ($total, $used, $free);
 while (<RESULT>) {
   warn("  $_") if ($verbose > 1);
-  next unless (m#^\-/\+\ buffers/cache:\s*(\d+)\s+(\d+)#);
-  $used = $1;
-  $free = $2;
+  # New `free` output from procps doesn't provide "buffers/cache" anymore, but
+  # provides a better estimate of available memory ("available" column).
+  $new_format = 1 if m{^\s+total\s+used\s+free\s+shared\s+buff/cache\s+available$};
+
+  if ($new_format and /^Mem:\s+(\d+)\s+\d+\s+\d+\s+\d+\s+\d+\s+(\d+)$/) {
+    $total = $1;
+    $free = $2; # available column
+    $used = $total - $free; # used is everything which is not available
+  } elsif (m#^\-/\+\ buffers/cache:\s*(\d+)\s+(\d+)#) {
+    $used = $1;
+    $free = $2;
+    $total = $used + $free;
+  }
 }
 
 close(RESULT);
@@ -117,7 +128,6 @@
 
 $np->nagios_exit('CRITICAL', "Unable to interpret $FREECMD output") if (!defined($free));
 
-my $total = $used + $free;
 if (defined($warning) && $warning =~ /^\d+%$/) {
   if ($warning) {
     $warning =~ s/%//;