diff --git a/niworkflows/func/util.py b/niworkflows/func/util.py
index 5879c946e85..a707a8fd55e 100644
--- a/niworkflows/func/util.py
+++ b/niworkflows/func/util.py
@@ -241,7 +241,7 @@ def init_bold_reference_wf(
     workflow.connect([
         (inputnode, val_sbref, [(("sbref_file", listify), "in_file")]),
         (val_sbref, merge_sbrefs, [("out_file", "in_files")]),
-        (merge_sbrefs, gen_avg, [("out_file", "sbref_file")]),
+        (merge_sbrefs, gen_avg, [("out_file", "in_file")]),
     ])
     # fmt: on
 
diff --git a/niworkflows/interfaces/images.py b/niworkflows/interfaces/images.py
index 065845435cf..1818cff44c0 100644
--- a/niworkflows/interfaces/images.py
+++ b/niworkflows/interfaces/images.py
@@ -191,7 +191,9 @@ def _run_interface(self, runtime):
 
 class _RobustAverageInputSpec(BaseInterfaceInputSpec):
     in_file = File(
-        exists=True, mandatory=True, desc="A 4D file to average through the last axis"
+        exists=True,
+        mandatory=True,
+        desc="Either a 3D reference or 4D file to average through the last axis"
     )
     t_mask = traits.List(traits.Bool, desc="List of selected timepoints to be averaged")
     mc_method = traits.Enum(