Add missing reST target to one heading in the tutorial
diff --git a/Doc/tutorial/interpreter.rst b/Doc/tutorial/interpreter.rst
index 8d743de..29afc50 100644
--- a/Doc/tutorial/interpreter.rst
+++ b/Doc/tutorial/interpreter.rst
@@ -169,6 +169,8 @@
 suppressed.
 
 
+.. _tut-source-encoding:
+
 Source Code Encoding
 --------------------