diff --git a/adder/adderutils/adderutils.go b/adder/adderutils/adderutils.go
index fb80c012..353e2de5 100644
--- a/adder/adderutils/adderutils.go
+++ b/adder/adderutils/adderutils.go
@@ -56,59 +56,59 @@ func AddMultipartHTTPHandler(
 	w.Header().Set("Connection", "close")
 
 	var wg sync.WaitGroup
-	if params.StreamChannels {
-		// handle stream-adding
-		// this should be the default.
-
-		// https://github.com/ipfs-shipyard/ipfs-companion/issues/600
-		w.Header().Set("X-Chunked-Output", "1")
-		// Used by go-ipfs to signal errors half-way through the stream.
-		w.Header().Set("Trailer", "X-Stream-Error")
-		w.WriteHeader(http.StatusOK)
+	if !params.StreamChannels {
+		// in this case we buffer responses in memory and
+		// return them as a valid JSON array.
 		wg.Add(1)
+		var bufOutput []interface{} // a slice of transformed AddedOutput
 		go func() {
 			defer wg.Done()
-			streamOutput(w, output, outputTransform)
+			bufOutput = buildOutput(output, outputTransform)
 		}()
+
+		enc := json.NewEncoder(w)
 		add := adder.New(dags, params, output)
 		root, err := add.FromMultipart(ctx, reader)
-		if err != nil {
+		if err != nil { // Send an error
 			logger.Error(err)
-			// Set trailer with error
-			w.Header().Set("X-Stream-Error", err.Error())
+			w.WriteHeader(http.StatusInternalServerError)
+			errorResp := api.Error{
+				Code:    http.StatusInternalServerError,
+				Message: err.Error(),
+			}
+
+			if err := enc.Encode(errorResp); err != nil {
+				logger.Error(err)
+			}
+			wg.Wait()
+			return root, err
 		}
 		wg.Wait()
+		w.WriteHeader(http.StatusOK)
+		enc.Encode(bufOutput)
 		return root, err
 	}
 
-	// Add buffering the AddedOutput (StreamChannels=false)
+	// handle stream-adding. This should be the default.
+
+	// https://github.com/ipfs-shipyard/ipfs-companion/issues/600
+	w.Header().Set("X-Chunked-Output", "1")
+	// Used by go-ipfs to signal errors half-way through the stream.
+	w.Header().Set("Trailer", "X-Stream-Error")
+	w.WriteHeader(http.StatusOK)
 	wg.Add(1)
-	var bufOutput []interface{} // a slice of transformed AddedOutput
 	go func() {
 		defer wg.Done()
-		bufOutput = buildOutput(w, output, outputTransform)
+		streamOutput(w, output, outputTransform)
 	}()
-
-	enc := json.NewEncoder(w)
 	add := adder.New(dags, params, output)
 	root, err := add.FromMultipart(ctx, reader)
-	if err != nil { // Send an error
+	if err != nil {
 		logger.Error(err)
-		w.WriteHeader(http.StatusInternalServerError)
-		errorResp := api.Error{
-			Code:    http.StatusInternalServerError,
-			Message: err.Error(),
-		}
-
-		if err := enc.Encode(errorResp); err != nil {
-			logger.Error(err)
-		}
-		wg.Wait()
-		return root, err
+		// Set trailer with error
+		w.Header().Set("X-Stream-Error", err.Error())
 	}
 	wg.Wait()
-	w.WriteHeader(http.StatusOK)
-	enc.Encode(bufOutput)
 	return root, err
 }
 
@@ -127,7 +127,7 @@ func streamOutput(w http.ResponseWriter, output chan *api.AddedOutput, transform
 	}
 }
 
-func buildOutput(w http.ResponseWriter, output chan *api.AddedOutput, transform func(*api.AddedOutput) interface{}) []interface{} {
+func buildOutput(output chan *api.AddedOutput, transform func(*api.AddedOutput) interface{}) []interface{} {
 	var finalOutput []interface{}
 	for v := range output {
 		finalOutput = append(finalOutput, transform(v))