diff --git a/pkgs/development/python-modules/dbf/default.nix b/pkgs/development/python-modules/dbf/default.nix
index f81b7d1c8bf9..a2f7b603b844 100644
--- a/pkgs/development/python-modules/dbf/default.nix
+++ b/pkgs/development/python-modules/dbf/default.nix
@@ -9,7 +9,7 @@ buildPythonPackage rec {
       sha256 = "01d71vya2x87f3kl9x0s8xp0n7wixn6ksrd054y7idq3n1mjaxzh";
     };
 
-    propagatedBuildInputs = [ aenum ] ++ stdenv.lib.optional (pythonOlder "3.4") [ enum34 ];
+    propagatedBuildInputs = [ aenum ] ++ stdenv.lib.optional (pythonOlder "3.4") enum34;
 
     doCheck = !isPy3k;
     # tests are not yet ported.
diff --git a/pkgs/development/python-modules/nipype/default.nix b/pkgs/development/python-modules/nipype/default.nix
index 13c35999cf94..ee3c16f01b66 100644
--- a/pkgs/development/python-modules/nipype/default.nix
+++ b/pkgs/development/python-modules/nipype/default.nix
@@ -79,7 +79,7 @@ buildPythonPackage rec {
     simplejson
     traits
     xvfbwrapper
-  ] ++ stdenv.lib.optional (!isPy3k) [
+  ] ++ stdenv.lib.optionals (!isPy3k) [
     configparser
     futures
     pathlib2 # darwin doesn't receive this transitively, but it is in install_requires
diff --git a/pkgs/development/python-modules/pytest-benchmark/default.nix b/pkgs/development/python-modules/pytest-benchmark/default.nix
index b43c00e42d9f..924f16694c53 100644
--- a/pkgs/development/python-modules/pytest-benchmark/default.nix
+++ b/pkgs/development/python-modules/pytest-benchmark/default.nix
@@ -19,7 +19,7 @@ buildPythonPackage rec {
     sha256 = "1hslzzinpwc1zqhbpllqh3sllmiyk69pcycl7ahr0rz3micgwczj";
   };
 
-  propagatedBuildInputs = [ pytest py-cpuinfo ] ++ lib.optional (pythonOlder "3.4") [ pathlib statistics ];
+  propagatedBuildInputs = [ pytest py-cpuinfo ] ++ lib.optionals (pythonOlder "3.4") [ pathlib statistics ];
 
   meta = {
     description = "Py.test fixture for benchmarking code";
diff --git a/pkgs/development/python-modules/quandl/default.nix b/pkgs/development/python-modules/quandl/default.nix
index fc4c192968f2..385c51bcd3b2 100644
--- a/pkgs/development/python-modules/quandl/default.nix
+++ b/pkgs/development/python-modules/quandl/default.nix
@@ -40,7 +40,7 @@ buildPythonPackage rec {
     python-dateutil
     six
     more-itertools
-  ] ++ lib.optional (!isPy3k) [
+  ] ++ lib.optionals (!isPy3k) [
     pyOpenSSL
     ndg-httpsclient
     pyasn1
diff --git a/pkgs/development/python-modules/tifffile/default.nix b/pkgs/development/python-modules/tifffile/default.nix
index 1fd33c5d7e4d..8aafc39fc344 100644
--- a/pkgs/development/python-modules/tifffile/default.nix
+++ b/pkgs/development/python-modules/tifffile/default.nix
@@ -23,7 +23,7 @@ buildPythonPackage rec {
   '';
 
   propagatedBuildInputs = [ numpy ]
-    ++ lib.optional isPy27 [ futures enum34 pathlib ];
+    ++ lib.optionals isPy27 [ futures enum34 pathlib ];
 
   meta = with lib; {
     description = "Read and write image data from and to TIFF files.";