diff --git a/lib/cast/uuid.js b/lib/cast/uuid.js
new file mode 100644
index 0000000000..6e296bf3e2
--- /dev/null
+++ b/lib/cast/uuid.js
@@ -0,0 +1,78 @@
+'use strict';
+
+const MongooseBuffer = require('../types/buffer');
+
+const UUID_FORMAT = /[0-9a-f]{8}-[0-9a-f]{4}-[0-9][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i;
+const Binary = MongooseBuffer.Binary;
+
+module.exports = function castUUID(value) {
+  if (value == null) {
+    return value;
+  }
+
+  function newBuffer(initbuff) {
+    const buff = new MongooseBuffer(initbuff);
+    buff._subtype = 4;
+    return buff;
+  }
+
+  if (typeof value === 'string') {
+    if (UUID_FORMAT.test(value)) {
+      return stringToBinary(value);
+    } else {
+      throw new Error(`"${value}" is not a valid UUID string`);
+    }
+  }
+
+  if (Buffer.isBuffer(value)) {
+    return newBuffer(value);
+  }
+
+  if (value instanceof Binary) {
+    return newBuffer(value.value(true));
+  }
+
+  // Re: gh-647 and gh-3030, we're ok with casting using `toString()`
+  // **unless** its the default Object.toString, because "[object Object]"
+  // doesn't really qualify as useful data
+  if (value.toString && value.toString !== Object.prototype.toString) {
+    if (UUID_FORMAT.test(value.toString())) {
+      return stringToBinary(value.toString());
+    }
+  }
+
+  throw new Error(`"${value}" cannot be casted to a UUID`);
+};
+
+module.exports.UUID_FORMAT = UUID_FORMAT;
+
+/**
+ * Helper function to convert the input hex-string to a buffer
+ * @param {String} hex The hex string to convert
+ * @returns {Buffer} The hex as buffer
+ * @api private
+ */
+
+function hex2buffer(hex) {
+  // use buffer built-in function to convert from hex-string to buffer
+  const buff = hex != null && Buffer.from(hex, 'hex');
+  return buff;
+}
+
+/**
+ * Convert a String to Binary
+ * @param {String} uuidStr The value to process
+ * @returns {MongooseBuffer} The binary to store
+ * @api private
+ */
+
+function stringToBinary(uuidStr) {
+  // Protect against undefined & throwing err
+  if (typeof uuidStr !== 'string') uuidStr = '';
+  const hex = uuidStr.replace(/[{}-]/g, ''); // remove extra characters
+  const bytes = hex2buffer(hex);
+  const buff = new MongooseBuffer(bytes);
+  buff._subtype = 4;
+
+  return buff;
+}
diff --git a/lib/schema/uuid.js b/lib/schema/uuid.js
index 1fbfc38654..0b3da55998 100644
--- a/lib/schema/uuid.js
+++ b/lib/schema/uuid.js
@@ -7,43 +7,13 @@
 const MongooseBuffer = require('../types/buffer');
 const SchemaType = require('../schemaType');
 const CastError = SchemaType.CastError;
+const castUUID = require('../cast/uuid');
 const utils = require('../utils');
 const handleBitwiseOperator = require('./operators/bitwise');
 
-const UUID_FORMAT = /[0-9a-f]{8}-[0-9a-f]{4}-[0-9][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i;
+const UUID_FORMAT = castUUID.UUID_FORMAT;
 const Binary = MongooseBuffer.Binary;
 
-/**
- * Helper function to convert the input hex-string to a buffer
- * @param {String} hex The hex string to convert
- * @returns {Buffer} The hex as buffer
- * @api private
- */
-
-function hex2buffer(hex) {
-  // use buffer built-in function to convert from hex-string to buffer
-  const buff = hex != null && Buffer.from(hex, 'hex');
-  return buff;
-}
-
-/**
- * Convert a String to Binary
- * @param {String} uuidStr The value to process
- * @returns {MongooseBuffer} The binary to store
- * @api private
- */
-
-function stringToBinary(uuidStr) {
-  // Protect against undefined & throwing err
-  if (typeof uuidStr !== 'string') uuidStr = '';
-  const hex = uuidStr.replace(/[{}-]/g, ''); // remove extra characters
-  const bytes = hex2buffer(hex);
-  const buff = new MongooseBuffer(bytes);
-  buff._subtype = 4;
-
-  return buff;
-}
-
 /**
  * Convert binary to a uuid string
  * @param {Buffer|Binary|String} uuidBin The value to process
@@ -109,44 +79,7 @@ SchemaUUID.prototype.constructor = SchemaUUID;
  * ignore
  */
 
-SchemaUUID._cast = function(value) {
-  if (value == null) {
-    return value;
-  }
-
-  function newBuffer(initbuff) {
-    const buff = new MongooseBuffer(initbuff);
-    buff._subtype = 4;
-    return buff;
-  }
-
-  if (typeof value === 'string') {
-    if (UUID_FORMAT.test(value)) {
-      return stringToBinary(value);
-    } else {
-      throw new CastError(SchemaUUID.schemaName, value, this.path);
-    }
-  }
-
-  if (Buffer.isBuffer(value)) {
-    return newBuffer(value);
-  }
-
-  if (value instanceof Binary) {
-    return newBuffer(value.value(true));
-  }
-
-  // Re: gh-647 and gh-3030, we're ok with casting using `toString()`
-  // **unless** its the default Object.toString, because "[object Object]"
-  // doesn't really qualify as useful data
-  if (value.toString && value.toString !== Object.prototype.toString) {
-    if (UUID_FORMAT.test(value.toString())) {
-      return stringToBinary(value.toString());
-    }
-  }
-
-  throw new CastError(SchemaUUID.schemaName, value, this.path);
-};
+SchemaUUID._cast = castUUID;
 
 /**
  * Attaches a getter for all UUID instances.
diff --git a/test/schema.uuid.test.js b/test/schema.uuid.test.js
index 77b7b2300f..e93538f78c 100644
--- a/test/schema.uuid.test.js
+++ b/test/schema.uuid.test.js
@@ -63,6 +63,8 @@ describe('SchemaUUID', function() {
     const errors = res.errors;
     assert.strictEqual(Object.keys(errors).length, 1);
     assert.ok(errors.x instanceof mongoose.Error.CastError);
+
+    assert.ok(errors.x.reason.message.includes('not a valid UUID string'), errors.x.reason.message);
   });
 
   it('should work with $in and $nin and $all', async function() {