diff --git a/pandoc.js b/pandoc.js
index ac92861..eddf173 100644
--- a/pandoc.js
+++ b/pandoc.js
@@ -112,9 +112,12 @@ exports.convert = function(type, input, types, callback) {
           //so that we have the target type in scope on('data') - love ya some asynch
           pandoc.stdout.targetType = types[i];
 
+          // Data may be batched. Ensure an empty placeholder is available for incremental collection.
+          res[types[i]] = '';
+
           pandoc.stdout.on('data', function(data) {
             //data will be a binary stream if you don't cast it to a string
-            res[this.targetType] = data + '';
+            res[this.targetType] += data + '';
           });
 
           pandoc.on('error', function(err) {