diff --git a/CUDA.make b/CUDA.make
index ef193df..bf376eb 100644
--- a/CUDA.make
+++ b/CUDA.make
@@ -1,6 +1,7 @@
+EXTRA_FLAGS?=-O3
 
 cuda-stream: main.cpp CUDAStream.cu
-	nvcc -std=c++11 -O3 -DCUDA $^ $(EXTRA_FLAGS) -o $@
+	nvcc -std=c++11 -DCUDA $^ $(EXTRA_FLAGS) -o $@
 
 .PHONY: clean
 clean: