diff --git a/libguile/exceptions.c b/libguile/exceptions.c
index 5c25ce6a9..54cec0fb0 100644
--- a/libguile/exceptions.c
+++ b/libguile/exceptions.c
@@ -32,7 +32,8 @@
 #include "eq.h"
 #include "eval.h"
 #include "fluids.h"
-#include "gsubr.h"
+#include "foreign.h"
+#include "gsubr-internal.h"
 #include "init.h"
 #include "keywords.h"
 #include "list.h"
@@ -40,7 +41,7 @@
 #include "numbers.h"
 #include "pairs.h"
 #include "ports.h"
-#include "smob.h"
+#include "programs.h"
 #include "stackchk.h"
 #include "stacks.h"
 #include "strings.h"
@@ -67,39 +68,51 @@
 
 /* First, some support for C bodies and exception handlers.  */
 
-static scm_t_bits tc16_thunk;
-static scm_t_bits tc16_exception_handler;
-
-SCM
-scm_c_make_thunk (scm_t_thunk thunk, void *data)
-{
-  SCM_RETURN_NEWSMOB2 (tc16_thunk, thunk, data);
-}
-
-SCM
-scm_c_make_exception_handler (scm_t_exception_handler handler, void *data)
-{
-  SCM_RETURN_NEWSMOB2 (tc16_exception_handler, handler, data);
-}
+static const uint32_t *call_thunk_code;
+static const uint32_t *call_exception_handler_code;
 
 static SCM
 call_thunk (SCM clo)
 {
-  scm_t_thunk thunk = (void*)SCM_SMOB_DATA (clo);
-  void *data = (void*)SCM_SMOB_DATA_2 (clo);
-
+  struct scm_program *p = scm_to_program (clo);
+  scm_t_thunk thunk = scm_to_pointer (scm_program_free_variable_ref (p, 0));
+  void *data = scm_to_pointer (scm_program_free_variable_ref (p, 1));
   return thunk (data);
 }
 
 static SCM
 call_exception_handler (SCM clo, SCM exn)
 {
-  scm_t_exception_handler handler = (void*)SCM_SMOB_DATA (clo);
-  void *data = (void*)SCM_SMOB_DATA_2 (clo);
+  struct scm_program *p = scm_to_program (clo);
+  scm_t_exception_handler handler =
+    scm_to_pointer (scm_program_free_variable_ref (p, 0));
+  void *data = scm_to_pointer (scm_program_free_variable_ref (p, 1));
 
   return handler (data, exn);
 }
 
+SCM
+scm_c_make_thunk (scm_t_thunk thunk, void *data)
+{
+  struct scm_program *ret =
+    scm_make_subr_from_code (SCM_I_CURRENT_THREAD, call_thunk_code,
+                             SCM_F_PROGRAM_IS_PRIMITIVE, 2);
+  scm_program_free_variable_set_x (ret, 0, scm_from_pointer (thunk, NULL));
+  scm_program_free_variable_set_x (ret, 1, scm_from_pointer (data, NULL));
+  return scm_from_program (ret);
+}
+
+SCM
+scm_c_make_exception_handler (scm_t_exception_handler handler, void *data)
+{
+  struct scm_program *ret =
+    scm_make_subr_from_code (SCM_I_CURRENT_THREAD, call_exception_handler_code,
+                             SCM_F_PROGRAM_IS_PRIMITIVE, 2);
+  scm_program_free_variable_set_x (ret, 0, scm_from_pointer (handler, NULL));
+  scm_program_free_variable_set_x (ret, 1, scm_from_pointer (data, NULL));
+  return scm_from_program (ret);
+}
+
 
 
 
@@ -493,11 +506,12 @@ sys_init_exceptions_x (SCM compound_exception_type,
 void
 scm_init_exceptions ()
 {
-  tc16_thunk = scm_make_smob_type ("thunk", 0);
-  scm_set_smob_apply (tc16_thunk, call_thunk, 0, 0, 0);
-
-  tc16_exception_handler = scm_make_smob_type ("exception-handler", 0);
-  scm_set_smob_apply (tc16_exception_handler, call_exception_handler, 1, 0, 0);
+  call_thunk_code =
+    scm_allocate_subr_code (scm_from_utf8_symbol ("thunk"), 0, 0, 0,
+                            call_thunk, SCM_F_SUBR_CLOSURE);
+  call_exception_handler_code =
+    scm_allocate_subr_code (scm_from_utf8_symbol ("exception-handler"), 1, 0, 0,
+                            call_exception_handler, SCM_F_SUBR_CLOSURE);
 
   exception_handler_fluid = scm_make_thread_local_fluid (SCM_BOOL_F);
   exception_epoch_fluid = scm_make_fluid_with_default (SCM_INUM1);