diff --git a/src/mathed/math_unknowninset.C b/src/mathed/math_unknowninset.C
index c54562514a..aadee3e4ee 100644
--- a/src/mathed/math_unknowninset.C
+++ b/src/mathed/math_unknowninset.C
@@ -11,7 +11,7 @@
 
 
 MathUnknownInset::MathUnknownInset(string const & nm, bool final, bool black)
-	: name_(nm), final_(final), black_(black)
+	: MathNestInset(1), name_(nm), final_(final), black_(black)
 {}
 
 
diff --git a/src/mathed/math_unknowninset.h b/src/mathed/math_unknowninset.h
index 1e6c2d6822..31a76d5c40 100644
--- a/src/mathed/math_unknowninset.h
+++ b/src/mathed/math_unknowninset.h
@@ -2,7 +2,7 @@
 #ifndef MATH_UNKNOWNINSET_H
 #define MATH_UNKNOWNINSET_H
 
-#include "math_diminset.h"
+#include "math_nestinset.h"
 
 #ifdef __GNUG__
 #pragma interface
@@ -11,7 +11,7 @@
 /**
  Unknowntions or LaTeX names for objects that we really don't know
  */
-class MathUnknownInset : public MathDimInset {
+class MathUnknownInset : public MathNestInset {
 public:
 	///
 	explicit MathUnknownInset(string const & name,