diff --git a/petprep/workflows/pet/hmc.py b/petprep/workflows/pet/hmc.py
index 660ecda5..1f60bb99 100644
--- a/petprep/workflows/pet/hmc.py
+++ b/petprep/workflows/pet/hmc.py
@@ -271,7 +271,9 @@ def num_files(filelist):
         name='smooth',
         iterfield=['in_file'],
     )
-    thresh = pe.MapNode(fsl.maths.Threshold(thresh=20), name='thresh', iterfield=['in_file'])
+    thresh = pe.MapNode(
+        fsl.maths.Threshold(thresh=20, use_robust_range=True), name='thresh', iterfield=['in_file']
+    )
 
     # Select reference frame
     start_frame = pe.Node(