diff --git a/global-requirements.txt b/global-requirements.txt
index 05d87ec3ca..59ec9d15e2 100644
--- a/global-requirements.txt
+++ b/global-requirements.txt
@@ -288,6 +288,8 @@ kafka-python>=0.9.2 # Apache-2.0
 keyring>=5.5.1  # MIT/PSF
 ldappool>=1.0;python_version=='2.7' # MPL
 mimic>=2.0.0  # Apache-2.0
+# Do not make mock conditional on Python version: we depend on newer code than
+# in [most] releases of the Python std library.
 mock>=1.2  # BSD
 mox>=0.5.3  # Apache-2.0
 mox3>=0.7.0  # Apache-2.0