diff --git a/src/mathed/InsetMathGrid.cpp b/src/mathed/InsetMathGrid.cpp
index f2d88a2bdf..3920677e60 100644
--- a/src/mathed/InsetMathGrid.cpp
+++ b/src/mathed/InsetMathGrid.cpp
@@ -26,6 +26,7 @@
 #include "CutAndPaste.h"
 #include "FuncRequest.h"
 #include "FuncStatus.h"
+#include "LaTeXFeatures.h"
 #include "TexRow.h"
 
 #include "frontends/Clipboard.h"
@@ -1237,6 +1238,19 @@ void InsetMathGrid::htmlize(HtmlStream & os) const
 }
 
 
+void InsetMathGrid::validate(LaTeXFeatures & features) const
+{
+	if (features.runparams().math_flavor == OutputParams::MathAsHTML
+	    && (nrows() > 1 || ncols() > 1)) {
+		// CSS taken from InsetMathCases
+		features.addCSSSnippet(
+			"table.mathtable{display: inline-block; text-align: center; border: none;"
+			"border-left: thin solid black; vertical-align: middle; padding-left: 0.5ex;}\n"
+			"table.mathtable td {text-align: left; border: none;}");
+	}
+}
+
+
 void InsetMathGrid::write(WriteStream & os) const
 {
 	write(os, 0, 0, nrows(), ncols());
diff --git a/src/mathed/InsetMathGrid.h b/src/mathed/InsetMathGrid.h
index e9ea396930..426d941f19 100644
--- a/src/mathed/InsetMathGrid.h
+++ b/src/mathed/InsetMathGrid.h
@@ -239,6 +239,8 @@ public:
 	///
 	void htmlize(HtmlStream &, std::string attrib) const;
 	///
+	void validate(LaTeXFeatures & features) const;
+	///
 	//void octave(OctaveStream &) const;
 
 protected: