diff --git a/modules/services/logging/syslogd.nix b/modules/services/logging/syslogd.nix
index 083568b51e30..bb088c250f6b 100644
--- a/modules/services/logging/syslogd.nix
+++ b/modules/services/logging/syslogd.nix
@@ -27,8 +27,6 @@ let
     *.*;mail.none;local1.none    -/var/log/messages
   '';
 
-  syslogdParameters = if cfg.enableNetworkInput then "-r " else "";
-
 in
 
 {
@@ -75,6 +73,15 @@ in
         '';
       };
 
+      extraParams = mkOption {
+        type = types.listOf types.string;
+        default = [ ];
+        example = [ "-m 0" ];
+        description = ''
+          Additional parameters passed to <command>syslogd</command>.
+        '';
+      };
+
     };
 
   };
@@ -84,6 +91,8 @@ in
 
   config = {
 
+    services.syslogd.extraParams = optional cfg.enableNetworkInput "-r";
+
     jobs.syslogd =
       { description = "Syslog daemon";
 
@@ -93,7 +102,7 @@ in
 
         daemonType = "fork";
 
-        exec = "${pkgs.sysklogd}/sbin/syslogd ${syslogdParameters} -f ${syslogConf}";
+        exec = "${pkgs.sysklogd}/sbin/syslogd ${toString cfg.extraParams} -f ${syslogConf}";
       };
 
   };
diff --git a/modules/testing/test-instrumentation.nix b/modules/testing/test-instrumentation.nix
index d1b3fe154d57..e2434aeb9ecb 100644
--- a/modules/testing/test-instrumentation.nix
+++ b/modules/testing/test-instrumentation.nix
@@ -92,6 +92,10 @@ in
     # Send all of /var/log/messages to the serial port.
     services.syslogd.extraConfig = "*.* /dev/ttyS0";
 
+    # Disable "-- MARK --" messages.  These prevent hanging tests from
+    # being killed after 1 hour of silence.
+    services.syslogd.extraParams = [ "-m 0" ];
+    
     # Don't run klogd.  Kernel messages appear on the serial console anyway.
     jobs.klogd.startOn = mkOverride 50 "";