diff --git a/DESCRIPTION b/DESCRIPTION
index dfa4ae6f..f95fb21c 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,8 +1,8 @@
 Package: pomp
 Type: Package
 Title: Statistical Inference for Partially Observed Markov Processes
-Version: 5.4.0.0
-Date: 2023-08-07
+Version: 5.4.1.0
+Date: 2023-08-08
 Authors@R: c(person(given=c("Aaron","A."),family="King",role=c("aut","cre"),email="kingaa@umich.edu",comment=c(ORCID="0000-0001-6159-3207")),
 	  person(given=c("Edward","L."),family="Ionides",role="aut",comment=c(ORCID="0000-0002-4190-0174"))	,
 	  person(given="Carles",family="Bretó",role="aut",comment=c(ORCID="0000-0003-4695-4902")),
diff --git a/inst/NEWS b/inst/NEWS
index 594a8a1a..0a190c06 100644
--- a/inst/NEWS
+++ b/inst/NEWS
@@ -1,5 +1,10 @@
 _N_e_w_s _f_o_r _p_a_c_k_a_g_e '_p_o_m_p'
 
+_C_h_a_n_g_e_s _i_n '_p_o_m_p' _v_e_r_s_i_o_n _5._4._1:
+
+        • C-level functions ‘set_pomp_userdata’ and
+          ‘unset_pomp_userdata’ are no longer exported.
+
 _C_h_a_n_g_e_s _i_n '_p_o_m_p' _v_e_r_s_i_o_n _5._3._1:
 
         • ‘stew’ now returns timing information by default.
diff --git a/inst/NEWS.Rd b/inst/NEWS.Rd
index c4525811..b9c301b8 100644
--- a/inst/NEWS.Rd
+++ b/inst/NEWS.Rd
@@ -1,5 +1,10 @@
 \name{NEWS}
 \title{News for package `pomp'}
+\section{Changes in \pkg{pomp} version 5.4.1}{
+  \itemize{
+    \item C-level functions \code{set_pomp_userdata} and \code{unset_pomp_userdata} are no longer exported.
+  }
+}
 \section{Changes in \pkg{pomp} version 5.3.1}{
   \itemize{
     \item \code{stew} now returns timing information by default.
diff --git a/inst/include/pomp_defines.h b/inst/include/pomp_defines.h
index 7dda6121..3c5cbe9c 100644
--- a/inst/include/pomp_defines.h
+++ b/inst/include/pomp_defines.h
@@ -33,8 +33,6 @@ typedef void table_lookup_t (lookup_table_t *tab, double x, double *y);
 typedef SEXP apply_probe_data_t (SEXP object, SEXP probes);
 typedef SEXP apply_probe_sim_t (SEXP object, SEXP nsim, SEXP params, SEXP probes, SEXP datval, SEXP gnsi);
 typedef SEXP systematic_resampling_t (SEXP weights);
-typedef void set_pomp_userdata_t (SEXP userdata);
-typedef void unset_pomp_userdata_t (void);
 typedef SEXP get_covariate_names_t (SEXP object);
 
 static R_INLINE SEXP makearray (int rank, const int *dim) {
diff --git a/src/init.c b/src/init.c
index 2fe6b8fc..1387106c 100644
--- a/src/init.c
+++ b/src/init.c
@@ -68,9 +68,6 @@ void R_init_pomp (DllInfo *info) {
   R_RegisterCCallable("pomp","apply_probe_sim",(DL_FUNC) &apply_probe_sim);
   R_RegisterCCallable("pomp","systematic_resampling",(DL_FUNC) &systematic_resampling);
   R_RegisterCCallable("pomp","randwalk_perturbation", (DL_FUNC) &randwalk_perturbation);
-  // THE FOLLOWING TWO FUNCTIONS WILL GO AWAY SOON
-  R_RegisterCCallable("pomp","set_pomp_userdata",(DL_FUNC) &set_pomp_userdata);
-  R_RegisterCCallable("pomp","unset_pomp_userdata",(DL_FUNC) &unset_pomp_userdata);
 
   // Register routines
   R_registerRoutines(info,NULL,callMethods,NULL,NULL);
diff --git a/src/pomp_defines.h b/src/pomp_defines.h
index 7dda6121..3c5cbe9c 100644
--- a/src/pomp_defines.h
+++ b/src/pomp_defines.h
@@ -33,8 +33,6 @@ typedef void table_lookup_t (lookup_table_t *tab, double x, double *y);
 typedef SEXP apply_probe_data_t (SEXP object, SEXP probes);
 typedef SEXP apply_probe_sim_t (SEXP object, SEXP nsim, SEXP params, SEXP probes, SEXP datval, SEXP gnsi);
 typedef SEXP systematic_resampling_t (SEXP weights);
-typedef void set_pomp_userdata_t (SEXP userdata);
-typedef void unset_pomp_userdata_t (void);
 typedef SEXP get_covariate_names_t (SEXP object);
 
 static R_INLINE SEXP makearray (int rank, const int *dim) {