diff --git a/indra/llaudio/llaudioengine.h b/indra/llaudio/llaudioengine.h
index 1f61cadb4b24415b0d00c6979617b7e88082ced7..1171b63f150146e2a1c5dfc33846fd674e8d7087 100644
--- a/indra/llaudio/llaudioengine.h
+++ b/indra/llaudio/llaudioengine.h
@@ -43,6 +43,7 @@
 
 #include "lllistener.h"
 #include "boost/unordered/unordered_flat_map.hpp"
+#include "boost/unordered_map.hpp"
 
 const F32 LL_WIND_UPDATE_INTERVAL = 0.1f;
 const F32 LL_WIND_UNDERWATER_CENTER_FREQ = 20.f;