diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index d2e4a17..1f265b2 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -10,6 +10,8 @@
 - Deprecated the VARBLOCK format and rsa.bigfile module due to security issues, see
     https://github.com/sybrenstuvel/python-rsa/issues/13
 - Integration with Travis-CI [1] and Coveralls [2]
+- Deprecated the old rsa._version133 and rsa._version200 submodules, they will be
+  completely removed in version 4.0.
 - Fixed bugs #12, #14, #27, #30
 
 [1] https://travis-ci.org/sybrenstuvel/python-rsa
diff --git a/doc/upgrading.rst b/doc/upgrading.rst
index c8a2d82..c21fa4b 100644
--- a/doc/upgrading.rst
+++ b/doc/upgrading.rst
@@ -3,7 +3,7 @@
 
 Previous versions of Python-RSA were less secure than the current
 version. In order to be able to gradually upgrade your software, those
-old versions are still available.
+old versions will be available until Python-RSA 4.0.
 
 To use version 1.3.3, use this::
 
@@ -26,6 +26,12 @@
 Those import statements *will create warnings* as they import much
 less secure code into your project.
 
+.. warning::
+
+    These modules are included to allow upgrading to the latest version
+    of Python-RSA, and not as a way to keep using those old versions.
+    They will be removed in version 4.0.
+
 The random padding introduced in version 3.0 made things much more
 secure, but also requires a larger key to encrypt the same message.
 You can either generate a new key with :py:func:`rsa.newkeys`, or use
diff --git a/rsa/_version133.py b/rsa/_version133.py
index b30b695..9115633 100644
--- a/rsa/_version133.py
+++ b/rsa/_version133.py
@@ -14,8 +14,11 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-"""RSA module
-pri = k[1]                               	//Private part of keys d,p,q
+"""Deprecated version of the RSA module
+
+.. deprecated:: 2.0
+
+    This submodule is deprecated and will be completely removed as of version 4.0.
 
 Module for calculating large primes, and RSA encryption, decryption,
 signing and verification. Includes generating public and private keys.
@@ -53,6 +56,9 @@
 import warnings
 warnings.warn('Insecure version of the RSA module is imported as %s, be careful'
         % __name__)
+warnings.warn('This submodule is deprecated and will be completely removed as of version 4.0.',
+              DeprecationWarning)
+
 
 def gcd(p, q):
     """Returns the greatest common divisor of p and q
diff --git a/rsa/_version200.py b/rsa/_version200.py
index 717b6ac..2436aa0 100644
--- a/rsa/_version200.py
+++ b/rsa/_version200.py
@@ -14,14 +14,11 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-"""RSA module
+"""Deprecated version of the RSA module
 
-Module for calculating large primes, and RSA encryption, decryption,
-signing and verification. Includes generating public and private keys.
+.. deprecated:: 3.0
 
-WARNING: this implementation does not use random padding, compression of the
-cleartext input to prevent repetitions, or other common security improvements.
-Use with care.
+    This submodule is deprecated and will be completely removed as of version 4.0.
 
 """
 
@@ -39,6 +36,8 @@
 # Display a warning that this insecure version is imported.
 import warnings
 warnings.warn('Insecure version of the RSA module is imported as %s' % __name__)
+warnings.warn('This submodule is deprecated and will be completely removed as of version 4.0.',
+              DeprecationWarning)
 
 
 def bit_size(number):