diff --git a/sys/modules/acpi/Makefile b/sys/modules/acpi/Makefile
index ce331e091533..4765a80125b5 100644
--- a/sys/modules/acpi/Makefile
+++ b/sys/modules/acpi/Makefile
@@ -50,9 +50,6 @@ CFLAGS+=-DACPI_MAX_THREADS=${ACPI_MAX_THREADS}
 .if ACPI_NO_SEMAPHORES
 CFLAGS+=-DACPI_NO_SEMAPHORES
 .endif
-.if SMP
-CFLAGS+=-DSMP
-.endif
 
 # Debugging support
 .if ACPI_DEBUG