diff --git a/src/mathed/math_boxinset.C b/src/mathed/math_boxinset.C
index 19ccbad82b..3c675a6028 100644
--- a/src/mathed/math_boxinset.C
+++ b/src/mathed/math_boxinset.C
@@ -8,6 +8,7 @@
 #include "math_support.h"
 #include "math_mathmlstream.h"
 #include "math_streamstr.h"
+#include "support/LOstream.h"
 
 
 MathBoxInset::MathBoxInset(string const & name)