diff --git a/packages/pg/lib/utils.js b/packages/pg/lib/utils.js
index ba51c82c8..fcf3c6686 100644
--- a/packages/pg/lib/utils.js
+++ b/packages/pg/lib/utils.js
@@ -37,7 +37,8 @@ function arrayString(val) {
       }
       result += '\\\\x' + item.toString('hex')
     } else {
-      result += escapeElement(prepareValue(item))
+      const prepared = prepareValue(item)
+      result += prepared == null ? 'NULL' : escapeElement(prepared)
     }
   }
   result += '}'
diff --git a/packages/pg/test/unit/utils-tests.js b/packages/pg/test/unit/utils-tests.js
index ff0d92944..debfaed89 100644
--- a/packages/pg/test/unit/utils-tests.js
+++ b/packages/pg/test/unit/utils-tests.js
@@ -181,6 +181,31 @@ test('prepareValue: complex array prepared properly', function () {
   assert.strictEqual(out, '{"{\\"x\\":42}","{\\"y\\":84}"}')
 })
 
+test('prepareValue: nullish custom array elements prepared as SQL NULL', function () {
+  for (const value of [null, undefined]) {
+    let calls = 0
+    const customType = {
+      toPostgres: function () {
+        calls++
+        return value
+      },
+    }
+    assert.strictEqual(utils.prepareValue([customType, 'NULL', '', 0, false]), '{NULL,"NULL","","0","false"}')
+    assert.strictEqual(calls, 1)
+    assert.strictEqual(utils.prepareValue([[customType], [customType]]), '{{NULL},{NULL}}')
+    assert.strictEqual(calls, 3)
+  }
+})
+
+test('prepareValue: chained nullish custom array elements prepared as SQL NULL', function () {
+  const customType = {
+    toPostgres: function () {
+      return { toPostgres: () => null }
+    },
+  }
+  assert.strictEqual(utils.prepareValue([customType]), '{NULL}')
+})
+
 test('prepareValue: date array prepared properly', function () {
   helper.setTimezoneOffset(-330)