diff --git a/usr.sbin/bhyve/acpi.h b/usr.sbin/bhyve/acpi.h
--- a/usr.sbin/bhyve/acpi.h
+++ b/usr.sbin/bhyve/acpi.h
@@ -57,7 +57,7 @@
 void	acpi_raise_gpe(struct vmctx *ctx, unsigned bit);
 int 	acpi_tables_add_device(const struct acpi_device *const dev);
 int	acpi_add_vcpu_affinity(int vcpuid, int domain);
-void	dsdt_line(const char *fmt, ...);
+void	dsdt_line(const char *fmt, ...) __printflike(1, 2);
 void	dsdt_fixed_ioport(uint16_t iobase, uint16_t length);
 void	dsdt_fixed_irq(uint8_t irq);
 void	dsdt_fixed_mem32(uint32_t base, uint32_t length);