diff --git a/fractal/tasks/image_labeling.py b/fractal/tasks/image_labeling.py
index 7d925b7d7..82a5e2101 100644
--- a/fractal/tasks/image_labeling.py
+++ b/fractal/tasks/image_labeling.py
@@ -183,10 +183,13 @@ def image_labeling(
     # Preliminary checks on multiscales
     multiscales = zattrs["multiscales"]
     if len(multiscales) > 1:
-        raise Exception(f"ERROR: There are {len(multiscales)} multiscales")
+        raise NotImplementedError(
+            f"Found {len(multiscales)} multiscales, "
+            "but only one is currently supported."
+        )
     if "coordinateTransformations" in multiscales[0].keys():
-        raise Exception(
-            "ERROR: coordinateTransformations at the multiscales "
+        raise NotImplementedError(
+            "global coordinateTransformations at the multiscales "
             "level are not currently supported"
         )
 
diff --git a/fractal/tasks/image_labeling_whole_well.py b/fractal/tasks/image_labeling_whole_well.py
index 3f77fa804..63a097ac8 100644
--- a/fractal/tasks/image_labeling_whole_well.py
+++ b/fractal/tasks/image_labeling_whole_well.py
@@ -87,8 +87,8 @@ def image_labeling_whole_well(
     if len(multiscales) > 1:
         raise Exception(f"ERROR: There are {len(multiscales)} multiscales")
     if "coordinateTransformations" in multiscales[0].keys():
-        raise Exception(
-            "ERROR: coordinateTransformations at the multiscales "
+        raise NotImplementedError(
+            "global coordinateTransformations at the multiscales "
             "level are not currently supported"
         )
 
diff --git a/fractal/tasks/lib_zattrs_utils.py b/fractal/tasks/lib_zattrs_utils.py
index 27e51695a..14fe7d7ef 100644
--- a/fractal/tasks/lib_zattrs_utils.py
+++ b/fractal/tasks/lib_zattrs_utils.py
@@ -19,8 +19,8 @@ def extract_zyx_pixel_sizes(zattrs_path: str, level: int = 0):
 
         # Check that there are no datasets-global transformations
         if "coordinateTransformations" in multiscales[0].keys():
-            raise Exception(
-                "ERROR: coordinateTransformations at the multiscales "
+            raise NotImplementedError(
+                "global coordinateTransformations at the multiscales "
                 "level are not currently supported"
             )