diff --git a/src/uproot/writing/identify.py b/src/uproot/writing/identify.py
index 1322b94ba..b1f35b852 100644
--- a/src/uproot/writing/identify.py
+++ b/src/uproot/writing/identify.py
@@ -265,7 +265,8 @@ def to_writable(obj):
             data = obj.values(flow=True)
             fSumw2 = (
                 obj.variances(flow=True)
-                if obj.storage_type == boost_histogram.storage.Weight
+                if boost_histogram is None
+                or obj.storage_type == boost_histogram.storage.Weight
                 else None
             )
 
@@ -293,7 +294,8 @@ def to_writable(obj):
 
             tmp = (
                 obj.variances()
-                if obj.storage_type == boost_histogram.storage.Weight
+                if boost_histogram is None
+                or obj.storage_type == boost_histogram.storage.Weight
                 else None
             )
             fSumw2 = None