diff --git a/mk/px4_targets.mk b/mk/px4_targets.mk
index 0fb263c37f..5bc6452051 100644
--- a/mk/px4_targets.mk
+++ b/mk/px4_targets.mk
@@ -70,10 +70,15 @@ endif
 
 .PHONY: module_mk
 module_mk:
+	$(v) echo "Building $(SKETCHBOOK)/module.mk"
 	$(RULEHDR)
 	$(v) echo "# Auto-generated file - do not edit" > $(SKETCHBOOK)/module.mk.new
 	$(v) echo "MODULE_COMMAND = ArduPilot" >> $(SKETCHBOOK)/module.mk.new
+ifeq (,$(MAKE_INC))
 	$(v) echo "SRCS = Build.$(SKETCH)/$(SKETCH).cpp $(SKETCHLIBSRCSRELATIVE)" >> $(SKETCHBOOK)/module.mk.new
+else
+	$(v) echo "SRCS = $(wildcard $(SRCROOT)/*.cpp) $(SKETCHLIBSRCSRELATIVE)" >> $(SKETCHBOOK)/module.mk.new
+endif
 	$(v) echo "MODULE_STACKSIZE = 4096" >> $(SKETCHBOOK)/module.mk.new
 	$(v) cmp $(SKETCHBOOK)/module.mk $(SKETCHBOOK)/module.mk.new 2>/dev/null || mv $(SKETCHBOOK)/module.mk.new $(SKETCHBOOK)/module.mk
 	$(v) rm -f $(SKETCHBOOK)/module.mk.new