diff --git a/lib/iris/util.py b/lib/iris/util.py
index e862e8055d..5f6ac166fe 100644
--- a/lib/iris/util.py
+++ b/lib/iris/util.py
@@ -25,7 +25,7 @@
 import numpy.ma as ma
 
 from iris._deprecation import warn_deprecated
-from iris._lazy_data import is_lazy_data
+from iris._lazy_data import as_concrete_data, is_lazy_data
 import iris.exceptions
 
 
@@ -364,7 +364,6 @@ def array_equal(array1, array2, withnans=False):
     def normalise_array(array):
         if not is_lazy_data(array):
             array = np.asarray(array)
-        # (All other np operations in array_equal() preserve array laziness).
         return array
 
     array1, array2 = normalise_array(array1), normalise_array(array2)
@@ -375,12 +374,22 @@ def normalise_array(array):
 
         if withnans and (array1.dtype.kind == "f" or array2.dtype.kind == "f"):
             nans1, nans2 = np.isnan(array1), np.isnan(array2)
-            if not np.all(nans1 == nans2):
-                eq = False  # simply fail
-            else:
-                eqs[nans1] = True  # fix NaNs; check all the others
+            eq = as_concrete_data(np.all(nans1 == nans2))
+
+            if eq:
+                eqs = as_concrete_data(eqs)
+                if not is_lazy_data(nans1):
+                    idxs = nans1
+                elif not is_lazy_data(nans2):
+                    idxs = nans2
+                else:
+                    idxs = as_concrete_data(nans1)
+
+                if np.any(idxs):
+                    eqs[idxs] = True
 
         if eq:
+            eqs = as_concrete_data(eqs)
             eq = np.all(eqs)  # check equal at all points
 
     return eq