diff --git a/flake.nix b/flake.nix
index 5d76568a..3fa02795 100644
--- a/flake.nix
+++ b/flake.nix
@@ -199,6 +199,21 @@
             };
           };
 
+          ReadonlyX = final.perlPackages.buildPerlModule {
+            pname = "ReadonlyX";
+            version = "1.04";
+            src = final.fetchurl {
+              url = "mirror://cpan/authors/id/S/SA/SANKO/ReadonlyX-1.04.tar.gz";
+              sha256 = "81bb97dba93ac6b5ccbce04a42c3590eb04557d75018773ee18d5a30fcf48188";
+            };
+            buildInputs = with final.perlPackages; [ ModuleBuildTiny TestFatal ];
+            meta = {
+              homepage = "https://github.com/sanko/readonly";
+              description = "Faster facility for creating read-only scalars, arrays, hashes";
+              license = final.lib.licenses.artistic2;
+            };
+          };
+
           TieHashMethod = final.buildPerlPackage {
               pname = "Tie-Hash-Method";
               version = "0.02";
@@ -472,7 +487,7 @@
                 ParallelForkManager
                 PerlCriticCommunity
                 PrometheusTinyShared
-                Readonly
+                ReadonlyX
                 SetScalar
                 SQLSplitStatement
                 Starman
diff --git a/src/lib/Hydra/Helper/CatalystUtils.pm b/src/lib/Hydra/Helper/CatalystUtils.pm
index 64e3c44f..925ed718 100644
--- a/src/lib/Hydra/Helper/CatalystUtils.pm
+++ b/src/lib/Hydra/Helper/CatalystUtils.pm
@@ -4,7 +4,7 @@ use utf8;
 use strict;
 use warnings;
 use Exporter;
-use Readonly;
+use ReadonlyX;
 use Nix::Store;
 use Hydra::Helper::Nix;
 
@@ -34,7 +34,7 @@ our @EXPORT = qw(
 
 
 # Columns from the Builds table needed to render build lists.
-Readonly our @buildListColumns => ('id', 'finished', 'timestamp', 'stoptime', 'project', 'jobset', 'job', 'nixname', 'system', 'buildstatus', 'releasename');
+Readonly::Array our @buildListColumns => ('id', 'finished', 'timestamp', 'stoptime', 'project', 'jobset', 'job', 'nixname', 'system', 'buildstatus', 'releasename');
 
 
 sub getBuild {
@@ -317,16 +317,16 @@ sub paramToList {
 
 
 # Security checking of filenames.
-Readonly our $pathCompRE    => "(?:[A-Za-z0-9-\+\._\$][A-Za-z0-9-\+\._\$:]*)";
-Readonly our $relPathRE     => "(?:$pathCompRE(?:/$pathCompRE)*)";
-Readonly our $relNameRE     => "(?:[A-Za-z0-9-_][A-Za-z0-9-\._]*)";
-Readonly our $attrNameRE    => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
-Readonly our $projectNameRE => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
-Readonly our $jobsetNameRE  => "(?:[A-Za-z_][A-Za-z0-9-_\.]*)";
-Readonly our $jobNameRE     => "(?:$attrNameRE(?:\\.$attrNameRE)*)";
-Readonly our $systemRE      => "(?:[a-z0-9_]+-[a-z0-9_]+)";
-Readonly our $userNameRE    => "(?:[a-z][a-z0-9_\.]*)";
-Readonly our $inputNameRE   => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
+Readonly::Scalar our $pathCompRE    => "(?:[A-Za-z0-9-\+\._\$][A-Za-z0-9-\+\._\$:]*)";
+Readonly::Scalar our $relPathRE     => "(?:$pathCompRE(?:/$pathCompRE)*)";
+Readonly::Scalar our $relNameRE     => "(?:[A-Za-z0-9-_][A-Za-z0-9-\._]*)";
+Readonly::Scalar our $attrNameRE    => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
+Readonly::Scalar our $projectNameRE => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
+Readonly::Scalar our $jobsetNameRE  => "(?:[A-Za-z_][A-Za-z0-9-_\.]*)";
+Readonly::Scalar our $jobNameRE     => "(?:$attrNameRE(?:\\.$attrNameRE)*)";
+Readonly::Scalar our $systemRE      => "(?:[a-z0-9_]+-[a-z0-9_]+)";
+Readonly::Scalar our $userNameRE    => "(?:[a-z][a-z0-9_\.]*)";
+Readonly::Scalar our $inputNameRE   => "(?:[A-Za-z_][A-Za-z0-9-_]*)";
 
 
 sub parseJobsetName {