diff --git a/ddclient.in b/ddclient.in
index e299a2e..4c4e6cf 100755
--- a/ddclient.in
+++ b/ddclient.in
@@ -156,8 +156,8 @@ our %config;
 #     it was just before the previous update attempt.  Values are synchronized from `%config` to
 #     `%recap` during each update attempt.
 #
-# The set of config change detection variables is currently hard-coded; all other recap variables
-# are assumed to be status variables.
+# A protocol's set of config change detection variables can be found in the protocol's
+# `force_update_if_changed` property; all other recap variables are assumed to be status variables.
 #
 # A note about terminology: This was previously named `%cache`, but "cache" implies that the
 # purpose is to reduce the cost or latency of data retrieval or computation, and that deletion only
@@ -168,8 +168,6 @@ our %config;
 # compatibility concerns with the public `--cache` option.)
 our %recap;
 
-our @recap_config_change_detection_vars = qw(static wildcard mx backupmx);
-
 my $result;
 my $saved_recap;
 my %saved_opt;
@@ -853,6 +851,7 @@ our %protocols = (
             %{$variables{'dyndns-common-defaults'}},
             'static' => setv(T_BOOL, 0, 1, 0, undef),
         },
+        'force_update_if_changed' => [qw(static wildcard mx backupmx)],
     },
     'dyndns2' => {
         'update'     => \&nic_dyndns2_update,
@@ -862,6 +861,7 @@ our %protocols = (
             %{$variables{'dyndns-common-defaults'}},
             'script' => setv(T_STRING, 0, 0, '/nic/update', undef),
         },
+        'force_update_if_changed' => [qw(wildcard mx backupmx)],
     },
     'easydns' => {
         'update'     => \&nic_easydns_update,
@@ -877,6 +877,7 @@ our %protocols = (
             'script'       => setv(T_STRING, 0, 0, '/dyn/generic.php',   undef),
             'wildcard'     => setv(T_BOOL,   0, 1, 0,                    undef),
         },
+        'force_update_if_changed' => [qw(wildcard mx backupmx)],
     },
     'freedns' => {
         'update'     => \&nic_freedns_update,
@@ -1487,8 +1488,9 @@ sub update_nics {
                 #     `update` sees consistent values between `%recap` and `%config`.  This reduces
                 #     the impact of Hyrum's Law; if a protocol needs a variable to be updated after
                 #     the `update` method is called then that behavior should be made explicit.
-                my $vars = $protocols{opt('protocol', $h)}{variables};
-                for my $v (@recap_config_change_detection_vars) {
+                my $protocol = $protocols{$p};
+                my $vars = $protocol->{variables};
+                for my $v (@{$protocol->{force_update_if_changed} // []}) {
                     next if !$vars->{$v} || !$vars->{$v}{recap};
                     if (defined(my $val = opt($v, $h))) {
                         $recap{$h}{$v} = $val;
@@ -3536,7 +3538,7 @@ sub nic_updateable {
                                     my $rv = $recap{$host}{$_};
                                     my $cv = opt($_, $host);
                                     defined($rv) && defined($cv) && $rv ne $cv;
-                                } @recap_config_change_detection_vars)) {
+                                } @{$protocol->{force_update_if_changed} // []})) {
         info("update forced because options changed: " . join(', ', @changed));
         $update = 1;