diff --git a/src/json.c b/src/json.c
index 928825e034..3aa6be7212 100644
--- a/src/json.c
+++ b/src/json.c
@@ -46,12 +46,14 @@ DEF_DLL_FN (size_t, json_array_size, (const json_t *array));
 DEF_DLL_FN (json_t *, json_object, (void));
 DEF_DLL_FN (int, json_object_set_new,
 	    (json_t *object, const char *key, json_t *value));
+DEF_DLL_FN (int, json_object_set_new_nocheck,
+	    (json_t *object, const char *key, json_t *value));
 DEF_DLL_FN (json_t *, json_null, (void));
 DEF_DLL_FN (json_t *, json_true, (void));
 DEF_DLL_FN (json_t *, json_false, (void));
 DEF_DLL_FN (json_t *, json_integer, (json_int_t value));
 DEF_DLL_FN (json_t *, json_real, (double value));
-DEF_DLL_FN (json_t *, json_stringn, (const char *value, size_t len));
+DEF_DLL_FN (json_t *, json_stringn_nocheck, (const char *value, size_t len));
 DEF_DLL_FN (char *, json_dumps, (const json_t *json, size_t flags));
 DEF_DLL_FN (int, json_dump_callback,
 	    (const json_t *json, json_dump_callback_t callback, void *data,
@@ -97,12 +99,13 @@ init_json_functions (void)
   LOAD_DLL_FN (library, json_array_size);
   LOAD_DLL_FN (library, json_object);
   LOAD_DLL_FN (library, json_object_set_new);
+  LOAD_DLL_FN (library, json_object_set_new_nocheck);
   LOAD_DLL_FN (library, json_null);
   LOAD_DLL_FN (library, json_true);
   LOAD_DLL_FN (library, json_false);
   LOAD_DLL_FN (library, json_integer);
   LOAD_DLL_FN (library, json_real);
-  LOAD_DLL_FN (library, json_stringn);
+  LOAD_DLL_FN (library, json_stringn_nocheck);
   LOAD_DLL_FN (library, json_dumps);
   LOAD_DLL_FN (library, json_dump_callback);
   LOAD_DLL_FN (library, json_integer_value);
@@ -131,12 +134,13 @@ init_json_functions (void)
 #define json_array_size fn_json_array_size
 #define json_object fn_json_object
 #define json_object_set_new fn_json_object_set_new
+#define json_object_set_new_nocheck fn_json_object_set_new_nocheck
 #define json_null fn_json_null
 #define json_true fn_json_true
 #define json_false fn_json_false
 #define json_integer fn_json_integer
 #define json_real fn_json_real
-#define json_stringn fn_json_stringn
+#define json_stringn_nocheck fn_json_stringn_nocheck
 #define json_dumps fn_json_dumps
 #define json_dump_callback fn_json_dump_callback
 #define json_integer_value fn_json_integer_value
@@ -394,9 +398,10 @@ lisp_to_json_toplevel_1 (Lisp_Object lisp,
                table test is not `equal'.  */
             if (json_object_get (json, key_str) != NULL)
               wrong_type_argument (Qjson_value_p, lisp);
-            int status = json_object_set_new (json, key_str,
-                                              lisp_to_json (HASH_VALUE (h, i),
-                                                            conf));
+            int status
+              = json_object_set_new_nocheck (json, key_str,
+                                             lisp_to_json (HASH_VALUE (h, i),
+                                                           conf));
             if (status == -1)
               {
                 /* A failure can be caused either by an invalid key or
@@ -508,12 +513,9 @@ lisp_to_json (Lisp_Object lisp, struct json_configuration *conf)
   else if (STRINGP (lisp))
     {
       Lisp_Object encoded = json_encode (lisp);
-      json_t *json = json_stringn (SSDATA (encoded), SBYTES (encoded));
+      json_t *json = json_stringn_nocheck (SSDATA (encoded), SBYTES (encoded));
       if (json == NULL)
         {
-          /* A failure can be caused either by an invalid string or by
-             low memory.  */
-          json_check_utf8 (encoded);
           json_out_of_memory ();
         }
       return json;