diff --git a/nipype/interfaces/afni/tests/test_auto_Unifize.py b/nipype/interfaces/afni/tests/test_auto_Unifize.py
index 6105a9d5c2..e5be64e70d 100644
--- a/nipype/interfaces/afni/tests/test_auto_Unifize.py
+++ b/nipype/interfaces/afni/tests/test_auto_Unifize.py
@@ -32,6 +32,8 @@ def test_Unifize_inputs():
     name_source='in_file',
     ),
     outputtype=dict(),
+    rbt=dict(argstr='-rbt %f %f %f',
+    ),
     scale_file=dict(argstr='-ssave %s',
     ),
     t2=dict(argstr='-T2',
diff --git a/nipype/interfaces/afni/utils.py b/nipype/interfaces/afni/utils.py
index 242b5077ee..3e03adda92 100644
--- a/nipype/interfaces/afni/utils.py
+++ b/nipype/interfaces/afni/utils.py
@@ -2329,6 +2329,14 @@ class UnifizeInputSpec(AFNICommandInputSpec):
         argstr='-EPI',
         requires=['no_duplo', 't2'],
         xor=['gm'])
+    rbt = traits.Tuple(
+        traits.Float(), traits.Float(), traits.Float(),
+        desc='Option for AFNI experts only.'
+             'Specify the 3 parameters for the algorithm:\n'
+             'R = radius; same as given by option \'-Urad\', [default=18.3]\n'
+             'b = bottom percentile of normalizing data range, [default=70.0]\n'
+             'r = top percentile of normalizing data range, [default=80.0]\n',
+        argstr='-rbt %f %f %f')
 
 
 class UnifizeOutputSpec(TraitedSpec):