diff --git a/src/buildMathML.js b/src/buildMathML.js
index cd29c2748..3fb89b047 100644
--- a/src/buildMathML.js
+++ b/src/buildMathML.js
@@ -265,7 +265,7 @@ var groupTypes = {
             // TODO(emily): Add a space in the middle of some of these
             // operators, like \limsup.
             node = new mathMLTree.MathNode(
-                "mo", [new mathMLTree.TextNode(group.value.body.slice(1))]);
+                "mi", [new mathMLTree.TextNode(group.value.body.slice(1))]);
         }
 
         return node;
diff --git a/test/katex-spec.js b/test/katex-spec.js
index 1b531d52d..6aab20d7d 100644
--- a/test/katex-spec.js
+++ b/test/katex-spec.js
@@ -1214,5 +1214,8 @@ describe("A MathML builder", function() {
 
         var text = getMathML("\\text{a}").children[0].children[0];
         expect(text.children[0].type).toEqual("mtext");
+
+        var textop = getMathML("\\sin").children[0].children[0];
+        expect(textop.children[0].type).toEqual("mi");
     });
 });