diff --git a/src/Makefile_obj.in b/src/Makefile_obj.in
index a0f995f8f..feca09f5f 100644
--- a/src/Makefile_obj.in
+++ b/src/Makefile_obj.in
@@ -326,6 +326,8 @@ V3Number_test: V3Number_test.o
 %__gen.cpp:	%.cpp $(ASTGEN) $(AST_DEFS) $(DFG_DEFS)
 	$(PYTHON3) $(ASTGEN) $(ASTGENFLAGS) $*.cpp
 
+.SECONDARY: V3Const__gen.o
+
 %.o:	%.cpp
 	$(OBJCACHE) ${CXX} ${CXXFLAGS} ${CPPFLAGSWALL} -c $< -o $@
 %.o:	%.c