diff --git a/Makefile b/Makefile
index 6a4b620..c4c5eba 100644
--- a/Makefile
+++ b/Makefile
@@ -267,7 +267,7 @@ endif
 	emcc -o $@ src/fp.cpp src/bn_c512.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=512 -DMCL_USE_WEB_CRYPTO_API -s DISABLE_EXCEPTION_CATCHING=1
 
 ../ecdsa-wasm/ecdsa_c.js: src/ecdsa_c.cpp src/fp.cpp include/mcl/ecdsa.hpp include/mcl/ecdsa.h Makefile
-	emcc -o $@ src/fp.cpp src/ecdsa_c.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=256
+	emcc -o $@ src/fp.cpp src/ecdsa_c.cpp $(EMCC_OPT) -DMCL_MAX_BIT_SIZE=256 -DMCL_USE_WEB_CRYPTO_API -s DISABLE_EXCEPTION_CATCHING=1
 
 mcl-wasm:
 	$(MAKE) ../mcl-wasm/mcl_c.js
diff --git a/src/ecdsa_c.cpp b/src/ecdsa_c.cpp
index e3e7f40..3b1d53c 100644
--- a/src/ecdsa_c.cpp
+++ b/src/ecdsa_c.cpp
@@ -16,6 +16,14 @@ static const Signature *cast(const ecdsaSignature *p) { return reinterpret_cast<
 static PrecomputedPublicKey *cast(ecdsaPrecomputedPublicKey *p) { return reinterpret_cast<PrecomputedPublicKey*>(p); }
 static const PrecomputedPublicKey *cast(const ecdsaPrecomputedPublicKey *p) { return reinterpret_cast<const PrecomputedPublicKey*>(p); }
 
+#ifdef __EMSCRIPTEN__
+// use these functions forcibly
+extern "C" ECDSA_DLL_API void ecdsaFree(void *p)
+{
+	free(p);
+}
+#endif
+
 int ecdsaInit(void)
 {
 	bool b;