diff --git a/development/HTML/HTML.notes b/development/HTML/HTML.notes
index 8628aad8d6..d609cb3fd0 100644
--- a/development/HTML/HTML.notes
+++ b/development/HTML/HTML.notes
@@ -44,8 +44,6 @@ Math
 	- Space: Needs checking.
 	- SpecialChar: Needs checking.
 	- Split: There are some alignment issues here, but it basically works.
-	- Substack: This is a stack of however many cells, all in a smaller style.
-		Probably do something with <mover>, again.
 	- Tabular: This is more or less a text-like table in math. Probably output it
 		as a table, but set the font.
 
diff --git a/src/mathed/InsetMathSubstack.cpp b/src/mathed/InsetMathSubstack.cpp
index fccdf7b3c3..56d253e3b2 100644
--- a/src/mathed/InsetMathSubstack.cpp
+++ b/src/mathed/InsetMathSubstack.cpp
@@ -128,15 +128,31 @@ void InsetMathSubstack::maple(MapleStream & os) const
 }
 
 
+void InsetMathSubstack::mathmlize(MathStream & os) const
+{
+	int movers = 0;
+	row_type const numrows = nrows();
+	for (row_type row = 0; row < nrows(); ++row) {
+		if (row < numrows - 1) {
+			movers ++;
+			os << MTag("munder");
+		}
+		os << MTag("mrow") << cell(index(row, 0)) << ETag("mrow");
+	}
+	for (int i = 1; i <= movers; ++i)
+		os << ETag("munder");
+}
+
+
 void InsetMathSubstack::htmlize(HtmlStream & os) const
 {
 	os << MTag("span", "class='substack'");
-	for (row_type row = 0; row < nrows(); ++row) 
+	for (row_type row = 0; row < nrows(); ++row)
 		os << MTag("span") << cell(index(row, 0)) << ETag("span");
 	os << ETag("span");
 }
 
-	
+
 void InsetMathSubstack::validate(LaTeXFeatures & features) const
 {
 	if (features.runparams().isLaTeX())
@@ -146,7 +162,7 @@ void InsetMathSubstack::validate(LaTeXFeatures & features) const
 			"span.substack{display: inline-block; vertical-align: middle; text-align:center; font-size: 75%;}\n"
 			"span.substack span{display: block;}\n"
 			"</style>");
-	
+
 	InsetMathGrid::validate(features);
 }
 
diff --git a/src/mathed/InsetMathSubstack.h b/src/mathed/InsetMathSubstack.h
index 612187ae89..822b0aa453 100644
--- a/src/mathed/InsetMathSubstack.h
+++ b/src/mathed/InsetMathSubstack.h
@@ -39,6 +39,8 @@ public:
 	///
 	void write(WriteStream & os) const;
 	///
+	void mathmlize(MathStream &) const;
+	///
 	void htmlize(HtmlStream &) const;
 	///
 	void normalize(NormalStream &) const;