diff --git a/TeXZilla.jison b/TeXZilla.jison
index ae6a21a..f479bec 100644
--- a/TeXZilla.jison
+++ b/TeXZilla.jison
@@ -71,6 +71,10 @@ function newMo(aContent, aLeftSpace, aRightSpace) {
   return tag;
 }
 
+function newSpace(aWidth) {
+   return "<mspace width=\"" + aWidth + "em\"/>";
+}
+
 function newScript(aUnderOver, aBase, aScriptBot, aScriptTop) {
   /* Create a new MathML script element. */
   if (aUnderOver) {
@@ -697,14 +701,14 @@ closedTerm
   | SLASH closedTerm {
     $$ = newTag("menclose", $2, "notation=\"updiagonalstrike\"");
   }
-  | QUAD { $$ = "<mspace width=\"1em\"/>"; }
-  | QQUAD { $$ = "<mspace width=\"2em\"/>"; }
-  | NEGSPACE { $$ = "<mspace width=\"negativethinmathspace\"/>"; }
-  | NEGMEDSPACE { $$ = "<mspace width=\"negativemediummathspace\"/>"; }
-  | NEGTHICKSPACE { $$ = "<mspace width=\"negativethickmathspace\"/>"; }
-  | THINSPACE { $$ = "<mspace width=\"thinmathspace\"/>"; }
-  | MEDSPACE { $$ = "<mspace width=\"mediummathspace\"/>"; }
-  | THICKSPACE { $$ = "<mspace width=\"thickmathspace\"/>"; }
+  | QUAD { $$ = newSpace(1); }
+  | QQUAD { $$ = newSpace(2); }
+  | NEGSPACE { $$ = newSpace(namedSpaceToEm("negativethinmathspace")); }
+  | NEGMEDSPACE { $$ = newSpace(namedSpaceToEm("negativemediummathspace")); }
+  | NEGTHICKSPACE { $$ = newSpace(namedSpaceToEm("negativethickmathspace")); }
+  | THINSPACE { $$ = newSpace(namedSpaceToEm("thinmathspace")); }
+  | MEDSPACE { $$ = newSpace(namedSpaceToEm("mediummathspace")); }
+  | THICKSPACE { $$ = newSpace(namedSpaceToEm("thickmathspace")); }
   | SPACE textArg textArg textArg {
     $$ = "<mspace height=\"." + $2 + "ex\" depth=\"." + $3 + "ex\" " +
                   "width=\"." + $4 + "em\"/>";
diff --git a/unit-tests.js b/unit-tests.js
index 442eb7c..de26db8 100644
--- a/unit-tests.js
+++ b/unit-tests.js
@@ -147,7 +147,7 @@ var tests = [
     /* \quad, \qquad */
     ["\\quad \\qquad", '<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mspace width="1em"/><mspace width="2em"/></mrow><annotation encoding="TeX">\\quad \\qquad</annotation></semantics></math>'],
     /* spaces */
-    ["\\! \\, \\: \\; \\medspace \\negspace \\negmedspace \\negthickspace \\thickspace \\thinspace", '<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mspace width="negativethinmathspace"/><mspace width="thinmathspace"/><mspace width="mediummathspace"/><mspace width="thickmathspace"/><mspace width="mediummathspace"/><mspace width="negativethinmathspace"/><mspace width="negativemediummathspace"/><mspace width="negativethickmathspace"/><mspace width="thickmathspace"/><mspace width="thinmathspace"/></mrow><annotation encoding="TeX">\\! \\, \\: \\; \\medspace \\negspace \\negmedspace \\negthickspace \\thickspace \\thinspace</annotation></semantics></math>'],
+    ["\\! \\, \\: \\; \\medspace \\negspace \\negmedspace \\negthickspace \\thickspace \\thinspace", '<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mspace width="0em"/><mspace width="0.16666666666666666em"/><mspace width="0.2222222222222222em"/><mspace width="0.2777777777777778em"/><mspace width="0.2222222222222222em"/><mspace width="0em"/><mspace width="-0.2222222222222222em"/><mspace width="-0.16666666666666666em"/><mspace width="0.2777777777777778em"/><mspace width="0.16666666666666666em"/></mrow><annotation encoding="TeX">\\! \\, \\: \\; \\medspace \\negspace \\negmedspace \\negthickspace \\thickspace \\thinspace</annotation></semantics></math>'],
     /* space */
     ["\\space{1}{2}{3}", '<math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mspace height=".1ex" depth=".2ex" width=".3em"/><annotation encoding="TeX">\\space{1}{2}{3}</annotation></semantics></math>'],
     /* mathraisebox */