diff --git a/Makefile.emscripten b/Makefile.emscripten
index 88637560b3..fa5d5b88e7 100644
--- a/Makefile.emscripten
+++ b/Makefile.emscripten
@@ -90,6 +90,7 @@ endif
 ifeq ($(HAVE_AL), 1)
    LDFLAGS += -lopenal
    DEFINES += -DHAVE_AL
+   ASYNC = 1
 endif
 
 ifneq ($(PTHREAD), 0)