diff --git a/pkgs/development/python-modules/cryptography/default.nix b/pkgs/development/python-modules/cryptography/default.nix
index dfbb14eb7e65..5e42774fdd97 100644
--- a/pkgs/development/python-modules/cryptography/default.nix
+++ b/pkgs/development/python-modules/cryptography/default.nix
@@ -20,9 +20,8 @@
 }:
 
 buildPythonPackage rec {
-  # also bump cryptography_vectors
   pname = "cryptography";
-  version = "2.5";
+  version = "2.5"; # Also update the hash in vectors.nix
 
   src = fetchPypi {
     inherit pname version;
diff --git a/pkgs/development/python-modules/cryptography_vectors/default.nix b/pkgs/development/python-modules/cryptography/vectors.nix
similarity index 77%
rename from pkgs/development/python-modules/cryptography_vectors/default.nix
rename to pkgs/development/python-modules/cryptography/vectors.nix
index f02a986ec023..86b16586f684 100644
--- a/pkgs/development/python-modules/cryptography_vectors/default.nix
+++ b/pkgs/development/python-modules/cryptography/vectors.nix
@@ -1,9 +1,9 @@
-{ buildPythonPackage, fetchPypi, lib }:
+{ buildPythonPackage, fetchPypi, lib, cryptography }:
 
 buildPythonPackage rec {
-  # also bump cryptography
   pname = "cryptography_vectors";
-  version = "2.5";
+  # The test vectors must have the same version as the cryptography package:
+  version = cryptography.version;
 
   src = fetchPypi {
     inherit pname version;
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index eb53f2dd5e02..0b7002cfe345 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -1481,7 +1481,7 @@ in {
 
   cryptography = callPackage ../development/python-modules/cryptography { };
 
-  cryptography_vectors = callPackage ../development/python-modules/cryptography_vectors { };
+  cryptography_vectors = callPackage ../development/python-modules/cryptography/vectors.nix { };
 
   curtsies = callPackage ../development/python-modules/curtsies { };