diff --git a/Code/Mantid/MantidQt/SliceViewer/src/LineViewer.cpp b/Code/Mantid/MantidQt/SliceViewer/src/LineViewer.cpp
index 8aa8131f22534b5806466679ad9c9c5c4f97cd1a..6933ad2426f7c3d95121af38ad146290c9bb3e53 100644
--- a/Code/Mantid/MantidQt/SliceViewer/src/LineViewer.cpp
+++ b/Code/Mantid/MantidQt/SliceViewer/src/LineViewer.cpp
@@ -256,6 +256,10 @@ void LineViewer::readTextboxes()
 
 //-----------------------------------------------------------------------------------------------
 /** Perform the 1D integration using the current parameters.
+ * Note that the algorithm is executed asynchronously (in the background),
+ * so this method may return before the integrated line
+ * workspace is ready.
+ *
  * @throw std::runtime_error if an error occurs.
  * */
 void LineViewer::apply()