diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index e05793c9b98fef5274e5db1163d9ce4f9a705bae..88ec193ed351066c0085682f9eb19f368b99b89d 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -469,7 +469,7 @@ struct sip_pkt;
 /*! \brief Parameters to the transmit_invite function */
 struct sip_invite_param {
 	const char *distinctive_ring;	/*!< Distinctive ring header */
-	char *osptoken;		/*!< OSP token for this call */
+	const char *osptoken;		/*!< OSP token for this call */
 	int addsipheaders;	/*!< Add extra SIP headers */
 	const char *uri_options;	/*!< URI options to add to the URI */
 	const char *vxml_url;		/*!< VXML url for Cisco phones */
@@ -1996,7 +1996,7 @@ static int sip_call(struct ast_channel *ast, char *dest, int timeout)
 	int res;
 	struct sip_pvt *p;
 #ifdef OSP_SUPPORT
-	char *osphandle = NULL;
+	const char *osphandle = NULL;
 #endif	
 	struct varshead *headp;
 	struct ast_var_t *current;
diff --git a/include/asterisk/astosp.h b/include/asterisk/astosp.h
index ee809bbc2c8c10738a61df63f7dfc8491411497e..9781ca6390b97f642f597b38e8df8b071733d915 100644
--- a/include/asterisk/astosp.h
+++ b/include/asterisk/astosp.h
@@ -43,6 +43,6 @@ int ast_osp_next(struct ast_osp_result *result, int cause);
 
 int ast_osp_terminate(int handle, int cause, time_t start, time_t duration);
 
-int ast_osp_validate(char *provider, char *token, int *handle, unsigned int *timeout, char *callerid, struct in_addr addr, char *extension);
+int ast_osp_validate(char *provider, char *token, int *handle, unsigned int *timeout, const char *callerid, struct in_addr addr, const char *extension);
 
 #endif /* _ASTERISK_OSP_H */
diff --git a/res/res_osp.c b/res/res_osp.c
index eb92f4862a4c32845682fc3ffdbf531c88fdcca7..339096a4a9114d43b2eef9807a2b86e36ef26fd9 100644
--- a/res/res_osp.c
+++ b/res/res_osp.c
@@ -452,7 +452,7 @@ static int loadPemPrivateKey(unsigned char *FileName, unsigned char *buffer, int
     return retVal;
 }
 
-int ast_osp_validate(char *provider, char *token, int *handle, unsigned int *timelimit, char *callerid, struct in_addr addr, char *extension)
+int ast_osp_validate(char *provider, char *token, int *handle, unsigned int *timelimit, const char *callerid, struct in_addr addr, const char *extension)
 {
 	char tmp[256]="", *l, *n;
 	char iabuf[INET_ADDRSTRLEN];