diff --git a/pkgs/development/python-modules/tensorflow-estimator/1/default.nix b/pkgs/development/python-modules/tensorflow-estimator/1/default.nix
index 39c667357c8..3e3d50bc6f4 100644
--- a/pkgs/development/python-modules/tensorflow-estimator/1/default.nix
+++ b/pkgs/development/python-modules/tensorflow-estimator/1/default.nix
@@ -6,6 +6,9 @@
 
 buildPythonPackage rec {
   pname = "tensorflow-estimator";
+  # This is effectively 1.15.0. Upstream tagged 1.15.0 by mistake before
+  # actually updating the version in setup.py, which is why this tag is called
+  # 1.15.1.
   version = "1.15.1";
   format = "wheel";