diff --git a/_pylibmcmodule.c b/_pylibmcmodule.c
index 9309bf4..1c02b7e 100644
--- a/_pylibmcmodule.c
+++ b/_pylibmcmodule.c
@@ -475,16 +475,17 @@ static PyObject *_PylibMC_RunSetCommandSingle(PylibMC_Client *self,
         _PylibMC_SetCommand f, char *fname, PyObject *args,
         PyObject *kwds) {
     /* function called by the set/add/etc commands */
-    static char *kws[] = { "key", "val", "time", "min_compress_len", NULL };
+    static char *kws[] = { "key", "val", "time", "use_custom_flag", "min_compress_len", NULL };
     PyObject *key;
     PyObject *value;
     unsigned int time = 0; /* this will be turned into a time_t */
+    unsigned int use_custom_flag = 0;
     unsigned int min_compress = 0;
     bool success = false;
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "SO|II", kws,
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "SO|III", kws,
                                      &key, &value,
-                                     &time, &min_compress)) {
+                                     &time, &use_custom_flag, &min_compress)) {
       return NULL;
     }
 
@@ -504,6 +505,7 @@ static PyObject *_PylibMC_RunSetCommandSingle(PylibMC_Client *self,
 
     success = _PylibMC_RunSetCommand(self, f, fname,
                                      &serialized, 1,
+                                     use_custom_flag,
                                      min_compress);
 
 cleanup:
@@ -526,14 +528,16 @@ static PyObject *_PylibMC_RunSetCommandMulti(PylibMC_Client* self,
     PyObject* key_prefix = NULL;
     unsigned int time = 0;
     unsigned int min_compress = 0;
+    unsigned int use_custom_flag = 0;
     PyObject * retval = NULL;
     size_t idx = 0;
 
-    static char *kws[] = { "keys", "time", "key_prefix", "min_compress_len", NULL };
+    static char *kws[] = { "keys", "time", "key_prefix", "use_custom_flag", "min_compress_len", NULL };
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O!|ISI", kws,
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O!|ISII", kws,
                                      &PyDict_Type, &keys,
                                      &time, &key_prefix,
+                                     &use_custom_flag,
                                      &min_compress)) {
         return NULL;
     }
@@ -584,6 +588,7 @@ static PyObject *_PylibMC_RunSetCommandMulti(PylibMC_Client* self,
 
     bool allsuccess = _PylibMC_RunSetCommand(self, f, fname,
                                              serialized, nkeys, 
+                                             use_custom_flag,
                                              min_compress);
 
     if (PyErr_Occurred() != NULL) {
@@ -810,6 +815,7 @@ static int _PylibMC_SerializeValue(PyObject* key_obj,
 static bool _PylibMC_RunSetCommand(PylibMC_Client* self,
                                    _PylibMC_SetCommand f, char *fname,
                                    pylibmc_mset* msets, size_t nkeys,
+                                   size_t use_custom_flag,
                                    size_t min_compress) {
     memcached_st* mc = self->mc;
     memcached_return rc = MEMCACHED_SUCCESS;
@@ -825,6 +831,10 @@ static bool _PylibMC_RunSetCommand(PylibMC_Client* self,
         char* value = mset->value;
         size_t value_len = mset->value_len;
         uint32_t flags = mset->flags;
+        
+        if (use_custom_flag) {
+            flags |= PYLIBMC_FLAG_CUSTOM;
+        }
 
 #ifdef USE_ZLIB
         char* compressed_value = NULL;
diff --git a/_pylibmcmodule.h b/_pylibmcmodule.h
index 03d57b7..07dc964 100644
--- a/_pylibmcmodule.h
+++ b/_pylibmcmodule.h
@@ -62,8 +62,9 @@ typedef ssize_t Py_ssize_t;
 #define PYLIBMC_FLAG_LONG    (1 << 2)
 /* Note: this is an addition! python-memcached doesn't handle bools. */
 #define PYLIBMC_FLAG_BOOL    (1 << 4)
+#define PYLIBMC_FLAG_CUSTOM  (1 << 5)
 #define PYLIBMC_FLAG_TYPES   (PYLIBMC_FLAG_PICKLE | PYLIBMC_FLAG_INTEGER | \
-                              PYLIBMC_FLAG_LONG | PYLIBMC_FLAG_BOOL)
+                              PYLIBMC_FLAG_LONG | PYLIBMC_FLAG_BOOL | PYLIBMC_FLAG_CUSTOM)
 /* Modifier flags */
 #define PYLIBMC_FLAG_ZLIB    (1 << 3)
 /* }}} */
@@ -278,6 +279,7 @@ static PyObject *_PylibMC_RunSetCommandMulti(PylibMC_Client* self,
 static bool _PylibMC_RunSetCommand(PylibMC_Client* self,
                                    _PylibMC_SetCommand f, char *fname,
                                    pylibmc_mset* msets, size_t nkeys,
+                                   size_t use_custom_flag,
                                    size_t min_compress);
 static int _PylibMC_Deflate(char* value, size_t value_len,
                             char** result, size_t *result_len);