diff --git a/nipype/interfaces/io.py b/nipype/interfaces/io.py
index bfa9353b98..142139548c 100644
--- a/nipype/interfaces/io.py
+++ b/nipype/interfaces/io.py
@@ -2935,12 +2935,12 @@ def __init__(self, infields=None, **kwargs):
                 "bold": {
                     "datatype": "func",
                     "suffix": "bold",
-                    "extensions": ["nii", ".nii.gz"],
+                    "extension": ["nii", ".nii.gz"],
                 },
                 "T1w": {
                     "datatype": "anat",
                     "suffix": "T1w",
-                    "extensions": ["nii", ".nii.gz"],
+                    "extension": ["nii", ".nii.gz"],
                 },
             }