diff --git a/lib/searpc-server.c b/lib/searpc-server.c
index 37a86da..5c1cb90 100644
--- a/lib/searpc-server.c
+++ b/lib/searpc-server.c
@@ -303,7 +303,7 @@ searpc_server_call_function (const char *svc_name,
 }
 
 char* 
-searpc_compute_signature(gchar *ret_type, int pnum, ...)
+searpc_compute_signature(const gchar *ret_type, int pnum, ...)
 {
     va_list ap;
     int i = 0;
diff --git a/lib/searpc-server.h b/lib/searpc-server.h
index d6b0562..61bbebc 100644
--- a/lib/searpc-server.h
+++ b/lib/searpc-server.h
@@ -96,6 +96,6 @@ gchar *searpc_server_call_function (const char *service,
  *
  * Compute function signature.
  */
-char* searpc_compute_signature (gchar *ret_type, int pnum, ...);
+char* searpc_compute_signature (const gchar *ret_type, int pnum, ...);
 
 #endif