diff --git a/gatchat/gatserver.c b/gatchat/gatserver.c
index 4ccea86d..b092a68c 100644
--- a/gatchat/gatserver.c
+++ b/gatchat/gatserver.c
@@ -1260,7 +1260,7 @@ gboolean g_at_server_set_debug(GAtServer *server, GAtDebugFunc func,
 	return TRUE;
 }
 
-gboolean g_at_server_register(GAtServer *server, char *prefix,
+gboolean g_at_server_register(GAtServer *server, const char *prefix,
 					GAtServerNotifyFunc notify,
 					gpointer user_data,
 					GDestroyNotify destroy_notify)
diff --git a/gatchat/gatserver.h b/gatchat/gatserver.h
index 5e663b75..a42c8b51 100644
--- a/gatchat/gatserver.h
+++ b/gatchat/gatserver.h
@@ -87,7 +87,7 @@ gboolean g_at_server_set_debug(GAtServer *server,
 					GAtDebugFunc func,
 					gpointer user_data);
 
-gboolean g_at_server_register(GAtServer *server, char *prefix,
+gboolean g_at_server_register(GAtServer *server, const char *prefix,
 					GAtServerNotifyFunc notify,
 					gpointer user_data,
 					GDestroyNotify destroy_notify);