diff --git a/direct/src/interval/cInterval.h b/direct/src/interval/cInterval.h
index a138ec7597..48d08dda89 100644
--- a/direct/src/interval/cInterval.h
+++ b/direct/src/interval/cInterval.h
@@ -189,7 +189,7 @@ private:
 };
 
 INLINE ostream &operator << (ostream &out, const CInterval &ival);
-ostream &operator << (ostream &out, CInterval::State state);
+EXPCL_DIRECT ostream &operator << (ostream &out, CInterval::State state);
 
 #include "cInterval.I"