diff --git a/src/mathed/InsetMathXArrow.h b/src/mathed/InsetMathXArrow.h
index f63eb2be19..722f4d58cd 100644
--- a/src/mathed/InsetMathXArrow.h
+++ b/src/mathed/InsetMathXArrow.h
@@ -39,6 +39,8 @@ public:
 	void validate(LaTeXFeatures & features) const;
 	///
 	InsetCode lyxCode() const { return MATH_XARROW_CODE; }
+	///
+	MathClass mathClass() const { return MC_REL; }
 
 private:
 	virtual Inset * clone() const;