diff --git a/metaflow/plugins/datatools/s3/s3.py b/metaflow/plugins/datatools/s3/s3.py
index aae53fb7be3..67224efc78b 100644
--- a/metaflow/plugins/datatools/s3/s3.py
+++ b/metaflow/plugins/datatools/s3/s3.py
@@ -495,6 +495,10 @@ class S3(object):
 
     @classmethod
     def get_root_from_config(cls, echo, create_on_absent=True):
+        if DATATOOLS_S3ROOT is None:
+            raise MetaflowS3URLException(
+                "DATATOOLS_S3ROOT is not configured when trying to use S3 storage"
+            )
         return DATATOOLS_S3ROOT
 
     def __init__(
@@ -512,6 +516,10 @@ def __init__(
 
         if run:
             # 1. use a (current) run ID with optional customizations
+            if DATATOOLS_S3ROOT is None:
+                raise MetaflowS3URLException(
+                    "DATATOOLS_S3ROOT is not configured when trying to use S3 storage"
+                )
             parsed = urlparse(DATATOOLS_S3ROOT)
             if not bucket:
                 bucket = parsed.netloc