diff --git a/doc/parameter.rst b/doc/parameter.rst
index 07789db38581..325352f195b6 100644
--- a/doc/parameter.rst
+++ b/doc/parameter.rst
@@ -192,6 +192,10 @@ Parameters for Tree Booster
     - ``cpu_predictor``: Multicore CPU prediction algorithm.
     - ``gpu_predictor``: Prediction using GPU. Default when ``tree_method`` is ``gpu_exact`` or ``gpu_hist``.
 
+* ``num_parallel_tree``, [default=1]
+  - Number of parallel trees constructed during each iteration. This
+     option is used to support boosted random forest
+
 Additional parameters for Dart Booster (``booster=dart``)
 =========================================================
 
diff --git a/src/gbm/gbtree.cc b/src/gbm/gbtree.cc
index d2def6663693..62886dfccaf4 100644
--- a/src/gbm/gbtree.cc
+++ b/src/gbm/gbtree.cc
@@ -52,7 +52,7 @@ struct GBTreeTrainParam : public dmlc::Parameter<GBTreeTrainParam> {
         .set_default(1)
         .set_lower_bound(1)
         .describe("Number of parallel trees constructed during each iteration."\
-                  " This option is used to support boosted random forest");
+                  " This option is used to support boosted random forest.");
     DMLC_DECLARE_FIELD(updater_seq)
         .set_default("grow_colmaker,prune")
         .describe("Tree updater sequence.");