diff --git a/tests/README.md b/tests/README.md
index 9bf2f819..edb0f530 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -16,4 +16,7 @@ work for me for some reason. Then, run the relevant batch file:
 
     mal_build_tests_emscripten.bat
     
-The output will be placed in the bin folder.
\ No newline at end of file
+The output will be placed in the bin folder. If you have output WASM it may not work when
+running the web page locally. To test you can run with something like this:
+
+    emrun bin/mal_test_0_emscripten.html
\ No newline at end of file
diff --git a/tests/mal_build_tests_emscripten.bat b/tests/mal_build_tests_emscripten.bat
index 83a3b69a..981aa286 100644
--- a/tests/mal_build_tests_emscripten.bat
+++ b/tests/mal_build_tests_emscripten.bat
@@ -1 +1 @@
-emcc ./mal_test_0.c -o ./bin/mal_test_0_emscripten.html
\ No newline at end of file
+emcc ./mal_test_0.c -o ./bin/mal_test_0_emscripten.html -O3
\ No newline at end of file