diff --git a/test/sim/tb_cxxrtl/Makefile b/test/sim/tb_cxxrtl/Makefile
index fbeb6fe..93ff3ba 100644
--- a/test/sim/tb_cxxrtl/Makefile
+++ b/test/sim/tb_cxxrtl/Makefile
@@ -16,7 +16,7 @@ SYNTH_CMD += write_cxxrtl build-$(DOTF)/dut.cpp
 
 CDEFINES_tb_multicore.f := WIDE_TIMER_IRQ
 
-build-$(DOTF)/dut.cpp: $(shell listfiles $(DOTF))
+build-$(DOTF)/dut.cpp: $(shell listfiles $(DOTF)) $(wildcard *.vh)
 	mkdir -p build-$(DOTF)
 	yosys -p '$(SYNTH_CMD)' 2>&1 > build-$(DOTF)/cxxrtl.log