diff --git a/tests/scripts/curves.pl b/tests/scripts/curves.pl
index 0bc4459..c9554e0 100755
--- a/tests/scripts/curves.pl
+++ b/tests/scripts/curves.pl
@@ -36,6 +36,7 @@
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
+    # use an exit code between 1 and 124 for git bisect (die returns 255)
     warn $_[0];
     exit 1;
 }