diff --git a/Makefile b/Makefile
index 1294d2f..1c86c08 100644
--- a/Makefile
+++ b/Makefile
@@ -588,7 +588,11 @@ OBJECTS := $(SOURCES_CXX:.cpp=.o) $(SOURCES_C:.c=.o)
 ifeq ($(DEBUG),1)
 FLAGS += -O0 -g
 else
-FLAGS += -O2 -DNDEBUG
+ifeq ($(platform), emscripten)
+   FLAGS += -O3 -DNDEBUG
+else
+   FLAGS += -O2 -DNDEBUG
+endif
 endif
 
 ifeq (,$(findstring msvc,$(platform)))