--- a/src/mod/endpoints/mod_gsmopen/gsmopen_protocol.cpp
+++ b/src/mod/endpoints/mod_gsmopen/gsmopen_protocol.cpp
@@ -104,6 +104,12 @@ int gettimeofday(struct timeval *tv, str
 /***************/
 #endif /* WIN32 */
 
+#if defined(FS_ICONV_INBUF_CONST)
+#define ICONV_INBUF_TYPE const char **
+#else
+#define ICONV_INBUF_TYPE char **
+#endif
+
 int gsmopen_serial_init(private_t *tech_pvt, int controldevice_speed)
 {
 	if (!tech_pvt)
@@ -2521,11 +2527,7 @@ int ucs2_to_utf8(private_t *tech_pvt, ch
 	DEBUGA_GSMOPEN("1 ciao in=%s, inleft=%d, out=%s, outleft=%d, converted=%s, utf8_out=%s\n",
 				   GSMOPEN_P_LOG, inbuf, (int) inbytesleft, outbuf, (int) outbytesleft, converted, utf8_out);
 
-#ifdef WIN32
-	iconv_res = iconv(iconv_format, (const char **) &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#else // WIN32
-	iconv_res = iconv(iconv_format, &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#endif // WIN32
+	iconv_res = iconv(iconv_format, (ICONV_INBUF_TYPE)&inbuf, &inbytesleft, &outbuf, &outbytesleft);
 	if (iconv_res == (size_t) -1) {
 		DEBUGA_GSMOPEN("2 ciao in=%s, inleft=%d, out=%s, outleft=%d, converted=%s, utf8_out=%s\n",
 					   GSMOPEN_P_LOG, inbuf, (int) inbytesleft, outbuf, (int) outbytesleft, converted, utf8_out);
@@ -2560,11 +2562,7 @@ int utf8_to_iso_8859_1(private_t *tech_p
 
 	DEBUGA_GSMOPEN("in=%s, inleft=%d, out=%s, outleft=%d, utf8_in=%s, iso_8859_1_out=%s\n",
 				   GSMOPEN_P_LOG, inbuf, (int) inbytesleft, outbuf, (int) outbytesleft, utf8_in, iso_8859_1_out);
-#ifdef WIN32
-	iconv_res = iconv(iconv_format, (const char **) &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#else // WIN32
-	iconv_res = iconv(iconv_format, &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#endif // WIN32
+	iconv_res = iconv(iconv_format, (ICONV_INBUF_TYPE)&inbuf, &inbytesleft, &outbuf, &outbytesleft);
 	if (iconv_res == (size_t) -1) {
 		DEBUGA_GSMOPEN("cannot translate in iso_8859_1 error: %s (errno: %d)\n", GSMOPEN_P_LOG, strerror(errno), errno);
 		return -1;
@@ -2597,11 +2595,7 @@ int iso_8859_1_to_utf8(private_t *tech_p
 	}
 
 	inbytesleft = strlen(iso_8859_1_in) * 2;
-#ifdef WIN32
-	iconv_res = iconv(iconv_format, (const char **) &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#else // WIN32
-	iconv_res = iconv(iconv_format, &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#endif // WIN32
+	iconv_res = iconv(iconv_format, (ICONV_INBUF_TYPE)&inbuf, &inbytesleft, &outbuf, &outbytesleft);
 	if (iconv_res == (size_t) -1) {
 		DEBUGA_GSMOPEN("ciao in=%s, inleft=%d, out=%s, outleft=%d, utf8_out=%s\n",
 					   GSMOPEN_P_LOG, inbuf, (int) inbytesleft, outbuf, (int) outbytesleft, utf8_out);
@@ -2642,11 +2636,7 @@ int utf8_to_ucs2(private_t *tech_pvt, ch
 
 	DEBUGA_GSMOPEN("in=%s, inleft=%d, out=%s, outleft=%d, utf8_in=%s, converted=%s\n",
 				   GSMOPEN_P_LOG, inbuf, (int) inbytesleft, outbuf, (int) outbytesleft, utf8_in, converted);
-#ifdef WIN32
-	iconv_res = iconv(iconv_format, (const char **) &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#else // WIN32
-	iconv_res = iconv(iconv_format, &inbuf, &inbytesleft, &outbuf, &outbytesleft);
-#endif // WIN32
+	iconv_res = iconv(iconv_format, (ICONV_INBUF_TYPE)&inbuf, &inbytesleft, &outbuf, &outbytesleft);
 	if (iconv_res == (size_t) -1) {
 		ERRORA("error: %s %d\n", GSMOPEN_P_LOG, strerror(errno), errno);
 		return -1;