diff --git a/CHANGELOG.md b/CHANGELOG.md
index f7c82a9..4038bf2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changes
 
+* 2.4.next in progress
+  * Fix [#509](https://github.com/seancorfield/honeysql/issues/509) by checking for `ident?` before checking keyword/symbol.
+
 * 2.4.1078 -- 2023-10-07
   * Address [#507](https://github.com/seancorfield/honeysql/issues/507) by clarifying formatting of `:cast` in **Special Syntax**.
   * Fix [#505](https://github.com/seancorfield/honeysql/issues/505) by rewriting the helper merge function to handle both keywords and symbols properly.
diff --git a/src/honey/sql.cljc b/src/honey/sql.cljc
index ff3e90d..b3a1645 100644
--- a/src/honey/sql.cljc
+++ b/src/honey/sql.cljc
@@ -936,7 +936,7 @@
 
 (defn- format-values [k xs]
   (let [first-xs (when (sequential? xs) (first (drop-while ident? xs)))]
-    (cond (contains? #{:default 'default} xs)
+    (cond (and (ident? xs) (contains? #{:default 'default} xs))
           [(str (sql-kw xs) " " (sql-kw k))]
           (empty? xs)
           [(str (sql-kw k) " ()")]
diff --git a/test/honey/sql_test.cljc b/test/honey/sql_test.cljc
index 987b7fb..911253a 100644
--- a/test/honey/sql_test.cljc
+++ b/test/honey/sql_test.cljc
@@ -1269,6 +1269,13 @@ ORDER BY id = ? DESC
   (is (= ["SELECT FOO(bar) AT TIME ZONE 'UTC'"]
          (sut/format {:select [[[:at-time-zone [:foo :bar] :UTC]]]}))))
 
+(deftest unhashable-value-509
+  (let [unhashable (reify Object
+                     (toString [_] "unhashable")
+                     (hashCode [_] (throw (ex-info "Unsupported" {}))))]
+    (is (= ["INSERT INTO table VALUES (?)" unhashable]
+           (sut/format {:insert-into :table :values [[unhashable]]})))))
+
 (comment
   ;; partial workaround for #407:
   (sut/format {:select :f.* :from [[:foo [:f :for :system-time]]] :where [:= :f.id 1]})