diff --git a/pkgs/development/perl-modules/mhonarc.patch b/pkgs/development/perl-modules/mhonarc.patch
new file mode 100644
index 00000000000..12b8cc2931b
--- /dev/null
+++ b/pkgs/development/perl-modules/mhonarc.patch
@@ -0,0 +1,26 @@
+diff --git a/lib/mhamain.pl b/lib/mhamain.pl
+index 80980a2..c1259ce 100644
+--- a/lib/mhamain.pl
++++ b/lib/mhamain.pl
+@@ -1562,7 +1562,7 @@ sub signal_catch {
+ ##
+ sub defineIndex2MsgId {
+     no warnings qw(deprecated);
+-    if (!defined(%Index2MsgId)) {
++    unless (%Index2MsgId) {
+ 	foreach (keys %MsgId) {
+ 	    $Index2MsgId{$MsgId{$_}} = $_;
+ 	}
+diff --git a/lib/mhopt.pl b/lib/mhopt.pl
+index 02fb05e..939109b 100644
+--- a/lib/mhopt.pl
++++ b/lib/mhopt.pl
+@@ -865,7 +865,7 @@ sub update_data_1_to_2 {
+ sub update_data_2_1_to_later {
+     no warnings qw(deprecated);
+     # we can preserve filter arguments
+-    if (defined(%main::MIMEFiltersArgs)) {
++    if (%main::MIMEFiltersArgs) {
+ 	warn qq/         preserving MIMEARGS...\n/;
+ 	%readmail::MIMEFiltersArgs = %main::MIMEFiltersArgs;
+ 	$IsDefault{'MIMEARGS'} = 0;
diff --git a/pkgs/top-level/perl-packages.nix b/pkgs/top-level/perl-packages.nix
index 8ef02140a32..48ab5094434 100644
--- a/pkgs/top-level/perl-packages.nix
+++ b/pkgs/top-level/perl-packages.nix
@@ -10669,6 +10669,9 @@ let
       url    = "http://dcssrv1.oit.uci.edu/indiv/ehood/release/MHonArc/tar/MHonArc-2.6.19.tar.gz";
       sha256 = "0ll3v93yji334zqp6xfzfxc0127pmjcznmai1l5q6dzawrs2igzq";
     };
+
+    patches = [ ../development/perl-modules/mhonarc.patch ];
+
     outputs = [ "out" "dev" ]; # no "devdoc"
 
     installTargets = "install";