diff --git a/.gitignore b/.gitignore
index 1ac66b755..4e52eb0fd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,7 +16,6 @@
 *.routes
 *.tr
 [D|U]l[A-Z][a-z]*Stats.txt
-seventh-packet-byte-count.png
 
 \#*#
 ~*
diff --git a/examples/tutorial/seventh.cc b/examples/tutorial/seventh.cc
index 983563a8a..f56db8c4c 100644
--- a/examples/tutorial/seventh.cc
+++ b/examples/tutorial/seventh.cc
@@ -58,6 +58,9 @@ NS_LOG_COMPONENT_DEFINE ("SeventhScriptExample");
 // So first, we create a socket and do the trace connect on it; then we pass
 // this socket into the constructor of our simple application which we then
 // install in the source node.
+//
+// NOTE: If this example gets modified, do not forget to update the .png figure
+// in src/stats/docs/seventh-packet-byte-count.png
 // ===========================================================================
 //
 class MyApp : public Application