diff --git a/nipype/interfaces/fsl/model.py b/nipype/interfaces/fsl/model.py
index 8c269caac7..15fb36f6c0 100644
--- a/nipype/interfaces/fsl/model.py
+++ b/nipype/interfaces/fsl/model.py
@@ -2245,7 +2245,7 @@ class RandomiseInputSpec(FSLCommandInputSpec):
         desc=("carry out Threshold-Free Cluster Enhancement with 2D " "optimisation"),
         argstr="--T2",
     )
-    f_only = traits.Bool(desc="calculate f-statistics only", argstr="--f_only")
+    f_only = traits.Bool(desc="calculate f-statistics only", argstr="--fonly")
     raw_stats_imgs = traits.Bool(
         desc="output raw ( unpermuted ) statistic images", argstr="-R"
     )
diff --git a/nipype/interfaces/fsl/tests/test_auto_Randomise.py b/nipype/interfaces/fsl/tests/test_auto_Randomise.py
index cf816c56de..9b0b74bf28 100644
--- a/nipype/interfaces/fsl/tests/test_auto_Randomise.py
+++ b/nipype/interfaces/fsl/tests/test_auto_Randomise.py
@@ -37,7 +37,7 @@ def test_Randomise_inputs():
             argstr="-S %.2f",
         ),
         f_only=dict(
-            argstr="--f_only",
+            argstr="--fonly",
         ),
         fcon=dict(
             argstr="-f %s",