diff --git a/gio/gregistrysettingsbackend.c b/gio/gregistrysettingsbackend.c
index 9f9d71857..b0e295a04 100644
--- a/gio/gregistrysettingsbackend.c
+++ b/gio/gregistrysettingsbackend.c
@@ -201,7 +201,7 @@ trace (const char *format,
  * equivalent function for g_warning because none of the registry errors can
  * result from programmer error (Microsoft programmers don't count), instead
  * they will mostly occur from people messing with the registry by hand. */
-static void
+static void G_GNUC_PRINTF (2, 3)
 g_message_win32_error (DWORD        result_code,
                        const gchar *format,
                       ...)
diff --git a/gmodule/gmodule-win32.c b/gmodule/gmodule-win32.c
index 5057d256e..fef4d893d 100644
--- a/gmodule/gmodule-win32.c
+++ b/gmodule/gmodule-win32.c
@@ -39,7 +39,7 @@
 #include <sys/cygwin.h>
 #endif
 
-static void
+static void G_GNUC_PRINTF (1, 2)
 set_error (const gchar *format,
 	   ...)
 {