diff --git a/src/featureforest/utils/data.py b/src/featureforest/utils/data.py
index c7aace6..dfa73a8 100644
--- a/src/featureforest/utils/data.py
+++ b/src/featureforest/utils/data.py
@@ -247,7 +247,7 @@ def is_image_rgb(image_data: ndarray) -> bool:
     Returns:
         bool: is image RGB(A)?
     """
-    return image_data.shape[-1] >= 3
+    return image_data.shape[-1] in [3, 4]
 
 
 def is_stacked(image_data: ndarray) -> bool: