diff --git a/smriprep/workflows/anatomical.py b/smriprep/workflows/anatomical.py
index d3bc607bbd..5b54fb11b7 100644
--- a/smriprep/workflows/anatomical.py
+++ b/smriprep/workflows/anatomical.py
@@ -1484,7 +1484,7 @@ def init_anat_template_wf(
     if gradunwarp_file:
         nds = [
             (
-                meta.get('NonlinearGradientCorrection', None)
+                not meta.get('NonlinearGradientCorrection', None)
                 or 'ND' in meta.get('ImageType', [])
                 or False
             )
@@ -1498,9 +1498,12 @@ def init_anat_template_wf(
             gradunwarp_file = None
     if gradunwarp_file:
         gradunwarp_ver = GradUnwarp.version()
-        workflow.__desc__ += f"""\
+        workflow.__desc__ = (
+            (workflow.__desc__ or '')
+            + f"""\
  {"Each" if num_files > 1 else "The"} {contrast} image was corrected for gradient
  non-linearity with `gradunwarp` [@gradunwarp] {gradunwarp_ver} [@gradunwarp]\n"""
+        )
         gradunwarp_wf = init_gradunwarp_wf('gradunward_T1w')
         gradunwarp_wf.inputs.inputnode.grad_file = gradunwarp_file
         # fmt:off
diff --git a/smriprep/workflows/tests/test_anatomical.py b/smriprep/workflows/tests/test_anatomical.py
index 5ba04a1e27..1df49a7860 100644
--- a/smriprep/workflows/tests/test_anatomical.py
+++ b/smriprep/workflows/tests/test_anatomical.py
@@ -20,7 +20,11 @@
 BASE_LAYOUT = {
     '01': {
         'anat': [
-            {'run': 1, 'suffix': 'T1w'},
+            {
+                'run': 1,
+                'suffix': 'T1w',
+                'metadata': {'ImageType': ['ND']},
+            },
             {'run': 2, 'suffix': 'T1w'},
             {'suffix': 'T2w'},
         ],