diff --git a/pkgs/development/interpreters/python/mk-python-derivation.nix b/pkgs/development/interpreters/python/mk-python-derivation.nix
index ef8ee4e5425..63ffdbb8c0a 100644
--- a/pkgs/development/interpreters/python/mk-python-derivation.nix
+++ b/pkgs/development/interpreters/python/mk-python-derivation.nix
@@ -101,10 +101,6 @@ toPythonModule (python.stdenv.mkDerivation (builtins.removeAttrs attrs [
     ${python.interpreter} ${./catch_conflicts}/catch_conflicts.py
   '' + attrs.postFixup or '''';
 
-  # Print fewer warnings so we have less noise in our logs
-  # The amount of warnings also caused builds to be terminated.
-  PYTHONWARNINGS="once";
-
   meta = {
     # default to python's platforms
     platforms = python.meta.platforms;
diff --git a/pkgs/development/python-modules/pytest/default.nix b/pkgs/development/python-modules/pytest/default.nix
index ad8c8d9ad0d..9412a750a9a 100644
--- a/pkgs/development/python-modules/pytest/default.nix
+++ b/pkgs/development/python-modules/pytest/default.nix
@@ -24,8 +24,7 @@ buildPythonPackage rec {
 
   checkPhase = ''
     runHook preCheck
-    # Re-enable warnings because the test suite relies on it.
-    PYTHONWARNINGS= $out/bin/py.test -x testing/
+    $out/bin/py.test -x testing/
     runHook postCheck
   '';