diff --git a/gtk/gtkmain.c b/gtk/gtkmain.c
index 645da6f8f2..bfee6da93b 100644
--- a/gtk/gtkmain.c
+++ b/gtk/gtkmain.c
@@ -849,9 +849,9 @@ gtk_get_option_group (gboolean open_default_display)
 gboolean
 gtk_init_with_args (int            *argc,
 		    char         ***argv,
-		    char           *parameter_string,  
+		    const char     *parameter_string,
 		    GOptionEntry   *entries,
-		    char           *translation_domain,
+		    const char     *translation_domain,
 		    GError        **error)
 {
   GOptionContext *context;
diff --git a/gtk/gtkmain.h b/gtk/gtkmain.h
index 975057e864..21de92ed42 100644
--- a/gtk/gtkmain.h
+++ b/gtk/gtkmain.h
@@ -99,9 +99,9 @@ gboolean gtk_init_check           (int    *argc,
   
 gboolean gtk_init_with_args       (int            *argc,
 				   char         ***argv,
-				   char           *parameter_string,
+				   const char     *parameter_string,
 				   GOptionEntry   *entries,
-				   char           *translation_domain,
+				   const char     *translation_domain,
 				   GError        **error);
 
 GOptionGroup *gtk_get_option_group (gboolean open_default_display);