diff --git a/Makefile b/Makefile
index 21f5f15..61330ce 100644
--- a/Makefile
+++ b/Makefile
@@ -244,7 +244,7 @@ else
 endif
 
 $(GEN_EXE): src/gen.cpp src/llvm_gen.hpp
-	$(CXX) -o $@ $< $(CFLAGS)
+	$(CXX) -o $@ $< $(CFLAGS) -DMCL_USE_VINT -DMCL_VINT_FIXED_BUFFER
 
 src/dump_code: src/dump_code.cpp src/fp.cpp src/fp_generator.hpp
 	$(CXX) -o $@ src/dump_code.cpp src/fp.cpp -g -I include -DMCL_DUMP_JIT -DMCL_MAX_BIT_SIZE=384 -DMCL_DONT_USE_OPENSSL -DMCL_USE_VINT -DMCL_SIZEOF_UNIT=8 -DMCL_VINT_FIXED_BUFFER