diff --git a/glib/gdatetime.h b/glib/gdatetime.h
index 65f9965ac..20167a60d 100644
--- a/glib/gdatetime.h
+++ b/glib/gdatetime.h
@@ -261,7 +261,7 @@ GDateTime *             g_date_time_to_utc                              (GDateTi
 
 GLIB_AVAILABLE_IN_ALL
 gchar *                 g_date_time_format                              (GDateTime      *datetime,
-                                                                         const gchar    *format) G_GNUC_MALLOC;
+                                                                         const gchar    *format) G_GNUC_MALLOC G_GNUC_STRFTIME (2);
 
 G_END_DECLS
 
diff --git a/glib/tests/gdatetime.c b/glib/tests/gdatetime.c
index a028f6d20..a434163c2 100644
--- a/glib/tests/gdatetime.c
+++ b/glib/tests/gdatetime.c
@@ -25,6 +25,14 @@
 #include <glib/gstdio.h>
 #include <locale.h>
 
+/* The tests below exercise invalid formats and y2k-unsafe formats,
+ * so we need to silence the warnings here to pass.
+ */
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wformat"
+#pragma GCC diagnostic ignored "-Wformat-y2k"
+#endif
+
 #define ASSERT_DATE(dt,y,m,d) G_STMT_START { \
   g_assert_nonnull ((dt)); \
   g_assert_cmpint ((y), ==, g_date_time_get_year ((dt))); \
diff --git a/tests/datetime.c b/tests/datetime.c
index ae46bbaea..16f4a95e2 100644
--- a/tests/datetime.c
+++ b/tests/datetime.c
@@ -18,6 +18,14 @@
 #include <locale.h>
 #include <glib/glib.h>
 
+/* The whole purpose of this test is to pass the command line argument
+ * to g_date_time_format(), so the format argument cannot be compile-
+ * time checked. Disable the inevitable compiler warning.
+ */
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif
+
 int
 main (int argc, char *argv[])
 {