diff --git a/vsdeband/placebo.py b/vsdeband/placebo.py
index 70284a0..63a7b8b 100644
--- a/vsdeband/placebo.py
+++ b/vsdeband/placebo.py
@@ -120,7 +120,7 @@ def _placebo(clip: vs.VideoNode, thr: float, grain: float, planes: Iterable[int]
 
         set_grn = set(grain)
 
-        if set_grn == {0} or clip.format.num_planes == 1:
+        if set_grn == {0} or clip.format.num_planes == 1 or (len(set_grn) and clip.format.color_family is vs.RGB):
             def_grain = grain[0] if clip.format.num_planes == 1 else 0
 
             debs = [_placebo(p, thr, def_grain, [0]) for p, thr in zip(split(clip), thr)]