diff --git a/lib/iris/pandas.py b/lib/iris/pandas.py
index 164fdd7859..780516f3ab 100644
--- a/lib/iris/pandas.py
+++ b/lib/iris/pandas.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2013 - 2017, Met Office
+# (C) British Crown Copyright 2013 - 2018, Met Office
 #
 # This file is part of Iris.
 #
@@ -55,7 +55,7 @@ def _add_iris_coord(cube, name, points, dim, calendar=None):
 
     # Convert pandas datetime objects to python datetime obejcts.
     if isinstance(points, DatetimeIndex):
-        points = np.array([i.to_datetime() for i in points])
+        points = np.array([i.to_pydatetime() for i in points])
 
     # Convert datetime objects to Iris' current datetime representation.
     if points.dtype == object:
diff --git a/requirements/core.txt b/requirements/core.txt
index 1af767d135..efc45cf55b 100644
--- a/requirements/core.txt
+++ b/requirements/core.txt
@@ -5,7 +5,7 @@
 
 cartopy
 matplotlib<1.9
-netcdf4
+netcdf4<1.4
 numpy
 scipy
 # pyke (not pip installable)  #conda: pyke