diff --git a/src/sourmash/tax/tax_utils.py b/src/sourmash/tax/tax_utils.py
index 8ad43c3b3..8e21d9f1c 100644
--- a/src/sourmash/tax/tax_utils.py
+++ b/src/sourmash/tax/tax_utils.py
@@ -1491,7 +1491,7 @@ def __init__(self, conn, *, table_name=None):
         # get available ranks...
         ranks = set()
         for column, rank in zip(self.columns, RankLineageInfo().taxlist):
-            query = f'SELECT COUNT({column}) FROM {self.table_name} WHERE {column} IS NOT NULL AND {column} != ""'
+            query = f"SELECT COUNT({column}) FROM {self.table_name} WHERE {column} IS NOT NULL AND {column} != ''"
             c.execute(query)
             (cnt,) = c.fetchone()
             if cnt: