diff --git a/DESCRIPTION b/DESCRIPTION
index a46c7716b..465b08af9 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: nanonext
 Type: Package
 Title: NNG (Nanomsg Next Gen) Lightweight Messaging Library
-Version: 1.3.2.9008
+Version: 1.3.2.9009
 Description: R binding for NNG (Nanomsg Next Gen), a successor to ZeroMQ. NNG is
     a socket library implementing 'Scalability Protocols', a reliable,
     high-performance standard for common communications patterns including
diff --git a/NEWS.md b/NEWS.md
index 79ca43fc6..d77bf7ca8 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,4 +1,4 @@
-# nanonext 1.3.2.9008 (development)
+# nanonext 1.3.2.9009 (development)
 
 #### New Features
 
diff --git a/R/utils.R b/R/utils.R
index 6882e1081..7016a028c 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -316,18 +316,20 @@ serial_config <- function(class, sfunc, ufunc, vec = FALSE)
 
 #' Set Serialization Marker
 #'
-#' Toggles the serialization marker on or off. Internal package function.
+#' Internal package function.
 #'
-#' @return NULL.
+#' @param x logical value.
+#'
+#' @return The logical value 'x' supplied.
 #'
 #' @examples
 #' .mark()
-#' .mark()
+#' .mark(FALSE)
 #'
 #' @keywords internal
 #' @export
 #'
-.mark <- function() .Call(rnng_set_marker)
+.mark <- function(x = TRUE) .Call(rnng_set_marker, x)
 
 #' Advances the RNG State
 #'
diff --git a/man/dot-mark.Rd b/man/dot-mark.Rd
index f02e94b45..28392a614 100644
--- a/man/dot-mark.Rd
+++ b/man/dot-mark.Rd
@@ -4,17 +4,20 @@
 \alias{.mark}
 \title{Set Serialization Marker}
 \usage{
-.mark()
+.mark(x = TRUE)
+}
+\arguments{
+\item{x}{logical value.}
 }
 \value{
-NULL.
+The logical value 'x' supplied.
 }
 \description{
-Toggles the serialization marker on or off. Internal package function.
+Internal package function.
 }
 \examples{
 .mark()
-.mark()
+.mark(FALSE)
 
 }
 \keyword{internal}
diff --git a/src/init.c b/src/init.c
index 7ebbef14f..95ab48fa3 100644
--- a/src/init.c
+++ b/src/init.c
@@ -178,7 +178,7 @@ static const R_CallMethodDef callMethods[] = {
   {"rnng_send", (DL_FUNC) &rnng_send, 5},
   {"rnng_send_aio", (DL_FUNC) &rnng_send_aio, 6},
   {"rnng_serial_config", (DL_FUNC) &rnng_serial_config, 4},
-  {"rnng_set_marker", (DL_FUNC) &rnng_set_marker, 0},
+  {"rnng_set_marker", (DL_FUNC) &rnng_set_marker, 1},
   {"rnng_set_opt", (DL_FUNC) &rnng_set_opt, 3},
   {"rnng_set_promise_context", (DL_FUNC) &rnng_set_promise_context, 2},
   {"rnng_signal_thread_create", (DL_FUNC) &rnng_signal_thread_create, 2},
diff --git a/src/nanonext.h b/src/nanonext.h
index 896f87f1c..7dbf7d416 100644
--- a/src/nanonext.h
+++ b/src/nanonext.h
@@ -362,7 +362,7 @@ SEXP rnng_request(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP rnng_send(SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP rnng_send_aio(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP rnng_serial_config(SEXP, SEXP, SEXP, SEXP);
-SEXP rnng_set_marker(void);
+SEXP rnng_set_marker(SEXP);
 SEXP rnng_set_opt(SEXP, SEXP, SEXP);
 SEXP rnng_set_promise_context(SEXP, SEXP);
 SEXP rnng_signal_thread_create(SEXP, SEXP);
diff --git a/src/utils.c b/src/utils.c
index ff04c0710..817908836 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -589,10 +589,10 @@ SEXP rnng_serial_config(SEXP klass, SEXP sfunc, SEXP ufunc, SEXP vec) {
 
 }
 
-SEXP rnng_set_marker(void) {
+SEXP rnng_set_marker(SEXP x) {
 
-  special_bit = special_bit ? (uint8_t) 0 : (uint8_t) 1;
-  return R_NilValue;
+  special_bit = (uint8_t) NANO_INTEGER(x);
+  return x;
 
 }
 
diff --git a/tests/tests.R b/tests/tests.R
index 3500191a8..c6f97141e 100644
--- a/tests/tests.R
+++ b/tests/tests.R
@@ -553,9 +553,9 @@ test_zero(dial(s, url = "inproc://disp/1"))
 test_true(wait(cv))
 test_zero(send(disp, TRUE, block = 500L))
 test_true(recv(s, block = 500L))
-test_null(.mark())
+test_true(.mark())
 test_zero(send(s, NULL, block = 500L))
-test_null(.mark())
+test_true(!.mark(FALSE))
 test_null(recv(disp, block = 500L))
 test_zero(reap(s))
 rm(disp)