diff --git a/src/webserver/database/sql.rs b/src/webserver/database/sql.rs
index f997065c..40f40d3c 100644
--- a/src/webserver/database/sql.rs
+++ b/src/webserver/database/sql.rs
@@ -604,6 +604,16 @@ mod tests {
         assert!(error.to_string().contains("HAVING"));
     }
 
+    #[test]
+    fn database_cannot_filter_by_computed_column_in_where() {
+        let FileStatement::Error(error) =
+            one("select sqlpage.url_encode(name) as enc from users where enc <> ''")
+        else {
+            panic!("expected rewrite error");
+        };
+        assert!(error.to_string().contains("WHERE"));
+    }
+
     #[test]
     fn database_cannot_group_by_computed_column_in_expression() {
         let FileStatement::Error(error) =
diff --git a/src/webserver/database/sql/rewrite.rs b/src/webserver/database/sql/rewrite.rs
index d137f26d..9ff49ea7 100644
--- a/src/webserver/database/sql/rewrite.rs
+++ b/src/webserver/database/sql/rewrite.rs
@@ -227,6 +227,7 @@ fn rewrite_top_level_projection(
     database_projection.append(&mut rewriter.private_projection);
     select.projection = database_projection;
 
+    reject_computed_alias_references("WHERE", select.selection.as_ref(), &computed_columns)?;
     reject_computed_group_by_references(&select.group_by, &computed_columns)?;
     reject_computed_alias_references("HAVING", select.having.as_ref(), &computed_columns)?;
     reject_computed_alias_references("QUALIFY", select.qualify.as_ref(), &computed_columns)?;