diff --git a/qemu/include/qemu/osdep.h b/qemu/include/qemu/osdep.h
index 8bdf4069..c3c61fe8 100644
--- a/qemu/include/qemu/osdep.h
+++ b/qemu/include/qemu/osdep.h
@@ -207,4 +207,13 @@ void qemu_anon_ram_free(void *ptr, size_t size);
  */
 unsigned long qemu_getauxval(unsigned long type);
 
+/* Starting on QEMU 2.5, qemu_hw_version() returns "2.5+" by default
+ * instead of QEMU_VERSION, so setting hw_version on MachineClass
+ * is no longer mandatory.
+ *
+ * Do NOT change this string, or it will break compatibility on all
+ * machine classes that don't set hw_version.
+ */
+#define QEMU_HW_VERSION "2.5+"
+
 #endif