diff --git a/.zenodo.json b/.zenodo.json
index a7333e6ec4..8fff817975 100644
--- a/.zenodo.json
+++ b/.zenodo.json
@@ -676,6 +676,11 @@
       "affiliation": "MIT, HMS",
       "name": "Ghosh, Satrajit",
       "orcid": "0000-0002-5312-6729"
+    },
+    {
+      "affiliation": "Holland Bloorview Kids Rehabilitation Hospital",
+      "name": "Tilley II, Steven",
+      "orcid": "0000-0003-4853-5082"
     }
   ],
   "keywords": [
diff --git a/nipype/interfaces/ants/registration.py b/nipype/interfaces/ants/registration.py
index c08c7646a9..9785b15954 100644
--- a/nipype/interfaces/ants/registration.py
+++ b/nipype/interfaces/ants/registration.py
@@ -1099,6 +1099,14 @@ def _format_registration(self):
                                                if len(moving_masks) > 1 else 0]
                 else:
                     moving_mask = 'NULL'
+                if (fixed_mask == 'NULL' or
+                        isinstance(fixed_mask, list) and 'NULL' in fixed_mask or
+                        moving_mask == 'NULL' or
+                        isinstance(moving_mask, list) and 'NULL' in moving_mask):
+                    print("CURRENT PATH: {}".format(os.getcwd()))
+                    if os.path.exists('NULL'):
+                        raise RuntimeError('NULL used as placeholder for no mask '
+                                           'but a file named NULL exists')
                 retval.append('--masks [ %s, %s ]' % (fixed_mask, moving_mask))
         return " ".join(retval)