gistfile1.diff

diff --git a/src/commands/math/commands.js b/src/commands/math/commands.js
index 483d591..1226d69 100644
--- a/src/commands/math/commands.js
+++ b/src/commands/math/commands.js
@@ -333,8 +333,8 @@ var SummationNotation = P(MathCommand, function(_, super_) {
     function simplify(latex) {
       return latex.length === 1 ? latex : '{' + (latex || ' ') + '}';
     }
-    return this.ctrlSeq + '_' + simplify(this.ends[L].latex()) +
-      '^' + simplify(this.ends[R].latex());
+    return this.ctrlSeq + '_' + simplify(this.blocks[0].latex()) +
+      '^' + simplify(this.blocks[1].latex()) + this.blocks[2].latex();
   };
   _.parser = function() {
     var string = Parser.string;
@@ -343,7 +343,7 @@ var SummationNotation = P(MathCommand, function(_, super_) {
     var block = latexMathParser.block;
 
     var self = this;
-    var blocks = self.blocks = [ MathBlock(), MathBlock() ];
+    var blocks = self.blocks = [ MathBlock(), MathBlock(), MathBlock() ];
     for (var i = 0; i < blocks.length; i += 1) {
       blocks[i].adopt(self, self.ends[R], 0);
     }
@@ -354,7 +354,9 @@ var SummationNotation = P(MathCommand, function(_, super_) {
         block.children().adopt(child, child.ends[R], 0);
         return succeed(self);
       });
-    }).many().result(self);
+    }).many().then(block).then(function(summand) {
+      summand.children().adopt(blocks[2]);
+    }).result(self);
   };
   _.finalizeTree = function() {
     this.downInto = this.ends[L];