diff --git a/Makefile b/Makefile
index 9e61368..bceebaf 100644
--- a/Makefile
+++ b/Makefile
@@ -218,7 +218,7 @@ $(EXPORTED_SHE_JS): ./include/mcl/she.h
 EXPORTED_SHE=$(shell cat $(SHE_TXT))
 
 docs/demo/mclshe.js: src/fp.cpp src/she_c256.cpp $(SHE_TXT) $(EXPORTED_SHE_JS)
-	emcc -o $@ src/fp.cpp src/she_c256.cpp -I./include -I./src -I../cybozulib/include -s WASM=1 -s "MODULARIZE=1" -s "EXPORTED_FUNCTIONS=[$(EXPORTED_SHE)]" -O3 -DNDEBUG -DMCLBN_FP_UNIT_SIZE=4 -DMCL_MAX_BIT_SIZE=256 -s DISABLE_EXCEPTION_CATCHING=0 -s NO_EXIT_RUNTIME=1
+	emcc -o $@ src/fp.cpp src/she_c256.cpp -I./include -I./src -I../cybozulib/include -s WASM=1 -s "MODULARIZE=1" -s "EXPORTED_FUNCTIONS=[$(EXPORTED_SHE)]" -O3 -DNDEBUG -DMCLBN_FP_UNIT_SIZE=4 -DMCL_MAX_BIT_SIZE=256 -s DISABLE_EXCEPTION_CATCHING=0 -s NO_EXIT_RUNTIME=1 -DMCLSHE_WIN_SIZE=8
 
 demo:
 	$(MAKE) docs/demo/mclshe.js
diff --git a/include/mcl/she.hpp b/include/mcl/she.hpp
index 4069fef..946611f 100644
--- a/include/mcl/she.hpp
+++ b/include/mcl/she.hpp
@@ -57,7 +57,10 @@ static thread_local std::random_device g_rg;
 #else
 static cybozu::RandomGenerator g_rg;
 #endif
-const size_t winSize = 10;
+#ifndef MCLSHE_WIN_SIZE
+	#define MCLSHE_WIN_SIZE 10
+#endif
+const size_t winSize = MCLSHE_WIN_SIZE;
 
 struct KeyCount {
 	uint32_t key;