diff --git a/Cython/Compiler/Code.py b/Cython/Compiler/Code.py
index 6220e3e730d..71b4825abbe 100644
--- a/Cython/Compiler/Code.py
+++ b/Cython/Compiler/Code.py
@@ -1,4 +1,5 @@
 # cython: language_level = 2
+# cython: auto_pickle=False
 #
 #   Code output module
 #
diff --git a/Cython/Compiler/Visitor.py b/Cython/Compiler/Visitor.py
index bbd5966a0e4..85e23b39f85 100644
--- a/Cython/Compiler/Visitor.py
+++ b/Cython/Compiler/Visitor.py
@@ -1,5 +1,6 @@
 # cython: infer_types=True
 # cython: language_level=3
+# cython: auto_pickle=False
 
 #
 #   Tree visitor and transform framework
diff --git a/Cython/Plex/Actions.py b/Cython/Plex/Actions.py
index 9e5f467f8dd..c88176e7161 100644
--- a/Cython/Plex/Actions.py
+++ b/Cython/Plex/Actions.py
@@ -1,3 +1,4 @@
+# cython: auto_pickle=False
 #=======================================================================
 #
 #   Python Lexical Analyser
diff --git a/Cython/Plex/Scanners.py b/Cython/Plex/Scanners.py
index a01a3aa9437..62f54728134 100644
--- a/Cython/Plex/Scanners.py
+++ b/Cython/Plex/Scanners.py
@@ -1,3 +1,4 @@
+# cython: auto_pickle=False
 #=======================================================================
 #
 #   Python Lexical Analyser
diff --git a/Cython/StringIOTree.py b/Cython/StringIOTree.py
index b406319c54d..d8239efeda9 100644
--- a/Cython/StringIOTree.py
+++ b/Cython/StringIOTree.py
@@ -1,3 +1,5 @@
+# cython: auto_pickle=False
+
 r"""
 Implements a buffer with insertion points. When you know you need to
 "get back" to a place and write more later, simply call insertion_point()