diff --git a/src/mathed/InsetMathBox.cpp b/src/mathed/InsetMathBox.cpp
index c5272c20e0..91c1a0ab2d 100644
--- a/src/mathed/InsetMathBox.cpp
+++ b/src/mathed/InsetMathBox.cpp
@@ -73,6 +73,14 @@ void InsetMathBox::infoize(odocstream & os) const
 }
 
 
+void InsetMathBox::validate(LaTeXFeatures & features) const
+{
+	if (name_ == "tag" || name_ == "tag*")
+		features.require("amsmath");
+	cell(0).validate(features);
+}
+
+
 
 /////////////////////////////////////////////////////////////////////
 //
diff --git a/src/mathed/InsetMathBox.h b/src/mathed/InsetMathBox.h
index b2525aa8d1..7138f25dce 100644
--- a/src/mathed/InsetMathBox.h
+++ b/src/mathed/InsetMathBox.h
@@ -36,6 +36,8 @@ public:
 	void normalize(NormalStream & ns) const;
 	///
 	void infoize(odocstream & os) const;
+	///
+	void validate(LaTeXFeatures & features) const;
 
 private:
 	Inset * clone() const { return new InsetMathBox(*this); }