diff --git a/README.md b/README.md
index 8073f53..d41ffb5 100644
--- a/README.md
+++ b/README.md
@@ -66,7 +66,8 @@ Different value types are escaped differently, here is how:
   the object. If the property's value is a function, it is skipped; if the
   property's value is an object, toString() is called on it and the returned
   value is used.
-* `undefined` / `null` are converted to `NULL`
+* JavaScript `null` is converted to MySQL `NULL`
+* JavaScript `undefined` is converted to MySQL `DEFAULT`
 * `NaN` / `Infinity` are left as-is. MySQL does not support these, and trying
   to insert them as values will trigger MySQL errors until they implement
   support.
diff --git a/lib/SqlString.js b/lib/SqlString.js
index 4dbf8fc..666450c 100644
--- a/lib/SqlString.js
+++ b/lib/SqlString.js
@@ -31,10 +31,14 @@ SqlString.escapeId = function escapeId(val, forbidQualified) {
 };
 
 SqlString.escape = function escape(val, stringifyObjects, timeZone) {
-  if (val === undefined || val === null) {
+  if (val === null) {
     return 'NULL';
   }
 
+  if (val === undefined) {
+    return 'DEFAULT';
+  }
+
   switch (typeof val) {
     case 'boolean': return (val) ? 'true' : 'false';
     case 'number': return val+'';
diff --git a/test/unit/test-SqlString.js b/test/unit/test-SqlString.js
index 7ac6358..c3102de 100644
--- a/test/unit/test-SqlString.js
+++ b/test/unit/test-SqlString.js
@@ -35,8 +35,8 @@ test('SqlString.escapeId', {
 });
 
 test('SqlString.escape', {
-  'undefined -> NULL': function() {
-    assert.equal(SqlString.escape(undefined), 'NULL');
+  'undefined -> DEFAULT': function() {
+    assert.equal(SqlString.escape(undefined), 'DEFAULT');
   },
 
   'null -> NULL': function() {