diff --git a/flight/targets/boards/simposix/firmware/Makefile b/flight/targets/boards/simposix/firmware/Makefile
index 70673a563..7d1f30ff4 100644
--- a/flight/targets/boards/simposix/firmware/Makefile
+++ b/flight/targets/boards/simposix/firmware/Makefile
@@ -63,6 +63,8 @@ FLIGHTLIB = ../../../../libraries
 FLIGHTLIBINC = $(FLIGHTLIB)/inc
 MATHLIB = $(FLIGHTLIB)/math
 MATHLIBINC = $(FLIGHTLIB)/math
+PIDLIB = $(FLIGHTLIB)/pid
+PIDLIBINC = $(FLIGHTLIB)/pid
 PIOSPOSIX = $(PIOS)/posix
 PIOSCOMMON = $(PIOS)/posix
 PIOSCORECOMMON = $(PIOS)/common
@@ -111,6 +113,7 @@ SRC += $(MATHLIB)/sin_lookup.c
 SRC += $(MATHLIB)/pid.c
 SRC += $(MATHLIB)/mathmisc.c
 SRC += $(MATHLIB)/butterworth.c
+CPPSRC += $(PIDLIB)/pidcontroldown.cpp
 
 SRC += $(PIOSCORECOMMON)/pios_task_monitor.c
 ifeq ($(USE_YAFFS),YES)
@@ -145,6 +148,7 @@ EXTRAINCDIRS  += $(OPUAVOBJINC)
 EXTRAINCDIRS  += $(UAVOBJSYNTHDIR)
 EXTRAINCDIRS  += $(FLIGHTLIBINC)
 EXTRAINCDIRS  += $(MATHLIBINC)
+EXTRAINCDIRS  += $(PIDLIBINC)
 EXTRAINCDIRS  += $(PIOSCOMMON)
 EXTRAINCDIRS  += $(CMSISDIR)
 EXTRAINCDIRS  += $(OPUAVSYNTHDIR)