diff --git a/tableone/validators.py b/tableone/validators.py
index cc83a1c..c8d10c7 100644
--- a/tableone/validators.py
+++ b/tableone/validators.py
@@ -156,5 +156,5 @@ def check_columns_exist(self, columns: list, categorical: list, continuous: list
         all_specified = cat_set.union(cont_set)
         if not all_specified.issubset(set(columns)):
             missing = list(all_specified - set(columns))
-            raise ValueError("Specified categorical/continuous columns not found in the DataFrame: "
-                             f"{missing}")
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+            raise ValueError("Specified categorical or continuous columns not found in the DataFrame: "
+                             f"{missing}. If the columns argument is specified, it must contain these variables.")
\ No newline at end of file