diff --git a/README.md b/README.md
index da258556f..a2048627e 100644
--- a/README.md
+++ b/README.md
@@ -82,7 +82,7 @@ This section shows how to install RTAB-Map ros-pkg on **ROS Hydro/Indigo/Jade/Ki
     $ git clone https://github.com/introlab/rtabmap.git rtabmap
     $ cd rtabmap/build
     $ cmake ..  [<---double dots included]
-    $ make
+    $ make -j6
     $ sudo make install
     ```
 
diff --git a/src/MsgConversion.cpp b/src/MsgConversion.cpp
index 6c95bd615..dc80a79a0 100644
--- a/src/MsgConversion.cpp
+++ b/src/MsgConversion.cpp
@@ -1991,7 +1991,7 @@ bool convertStereoMsg(
 	if(leftImageMsg->encoding.compare(sensor_msgs::image_encodings::TYPE_8UC1) == 0 ||
 	   leftImageMsg->encoding.compare(sensor_msgs::image_encodings::MONO8) == 0)
 	{
-		left = leftImageMsg->image;
+		left = leftImageMsg->image.clone();
 	}
 	else if(leftImageMsg->encoding.compare(sensor_msgs::image_encodings::MONO16) == 0)
 	{
@@ -2004,7 +2004,7 @@ bool convertStereoMsg(
 	if(rightImageMsg->encoding.compare(sensor_msgs::image_encodings::TYPE_8UC1) == 0 ||
 	   rightImageMsg->encoding.compare(sensor_msgs::image_encodings::MONO8) == 0)
 	{
-		right = rightImageMsg->image;
+		right = rightImageMsg->image.clone();
 	}
 	else
 	{