diff --git a/nipype/pipeline/engine/tests/test_join.py b/nipype/pipeline/engine/tests/test_join.py
index 2fe5f70564..da24adee37 100644
--- a/nipype/pipeline/engine/tests/test_join.py
+++ b/nipype/pipeline/engine/tests/test_join.py
@@ -2,6 +2,7 @@
 # vi: set ft=python sts=4 ts=4 sw=4 et:
 """Tests for join expansion
 """
+import operator
 import pytest
 
 from .... import config
@@ -640,14 +641,11 @@ def sq(x):
 def test_join_nestediters(tmpdir):
     tmpdir.chdir()
 
-    def exponent(x, p):
-        return x**p
-
     wf = pe.Workflow("wf", base_dir=tmpdir.strpath)
 
     xs = pe.Node(IdentityInterface(["x"]), iterables=[("x", [1, 2])], name="xs")
     ps = pe.Node(IdentityInterface(["p"]), iterables=[("p", [3, 4])], name="ps")
-    exp = pe.Node(Function(function=exponent), name="exp")
+    exp = pe.Node(Function(function=operator.pow), name="exp")
     exp_joinx = pe.JoinNode(
         Merge(1, ravel_inputs=True),
         name="exp_joinx",
diff --git a/nipype/pipeline/engine/utils.py b/nipype/pipeline/engine/utils.py
index d947735cb0..40994dcc80 100644
--- a/nipype/pipeline/engine/utils.py
+++ b/nipype/pipeline/engine/utils.py
@@ -4,6 +4,7 @@
 import os
 import sys
 import pickle
+import operator
 from collections import defaultdict
 import re
 from copy import deepcopy
@@ -612,7 +613,7 @@ def count_iterables(iterables, synchronize=False):
     Otherwise, the count is the product of the iterables value
     list sizes.
     """
-    op = max if synchronize else lambda x, y: x * y
+    op = max if synchronize else operator.mul
     return reduce(op, [len(func()) for _, func in list(iterables.items())])