diff --git a/MongoDB/include/Poco/MongoDB/ObjectId.h b/MongoDB/include/Poco/MongoDB/ObjectId.h
index 59845dcf5..aa85a2907 100644
--- a/MongoDB/include/Poco/MongoDB/ObjectId.h
+++ b/MongoDB/include/Poco/MongoDB/ObjectId.h
@@ -46,8 +46,12 @@ class MongoDB_API ObjectId
 public:
 	typedef SharedPtr<ObjectId> Ptr;
 
-	ObjectId(const std::string& id = "");
-		/// Constructor
+	ObjectId(const std::string& id);
+		/// Constructor. The string must contain a hexidecimal representation
+		/// of an object id. This means a string of 24 characters.
+
+	ObjectId(const ObjectId& copy);
+		/// Copy constructor.
 
 	virtual ~ObjectId();
 		/// Destructor
@@ -61,10 +65,19 @@ public:
 		/// of the ID char array.
 
 private:
+
+	ObjectId();
+		/// Constructor. Creates an empty Id
+
 	unsigned char _id[12];
 
 	friend class BSONWriter;
 	friend class BSONReader;
+	friend class Document;
+	
+	static int fromHex(char c);
+	
+	static char fromHex(const char* c);
 };
 
 
@@ -79,6 +92,21 @@ inline Timestamp ObjectId::timestamp() const
 	return Timestamp::fromEpochTime((time_t) time);
 }
 
+inline int ObjectId::fromHex(char c)
+{
+	if ( '0' <= c && c <= '9' )
+		return c - '0';
+	if ( 'a' <= c && c <= 'f' )
+		return c - 'a' + 10;
+	if ( 'A' <= c && c <= 'F' )
+		return c - 'A' + 10;
+	return 0xff;
+}
+
+inline char ObjectId::fromHex(const char* c)
+{
+	return (char)((fromHex(c[0]) << 4 ) | fromHex(c[1]));
+}
 
 // BSON Embedded Document
 // spec: ObjectId
@@ -89,7 +117,7 @@ struct ElementTraits<ObjectId::Ptr>
 
 	static std::string toString(const ObjectId::Ptr& id,
 		int indent = 0,
-		const std::string& fmt = "%x")
+		const std::string& fmt = "%02x")
 	{
 		return id->toString(fmt);
 	}
diff --git a/MongoDB/src/ObjectId.cpp b/MongoDB/src/ObjectId.cpp
index 257fa1c18..0111c7af7 100644
--- a/MongoDB/src/ObjectId.cpp
+++ b/MongoDB/src/ObjectId.cpp
@@ -15,7 +15,6 @@
 // SPDX-License-Identifier:	BSL-1.0
 //
 
-
 #include "Poco/MongoDB/ObjectId.h"
 #include "Poco/Format.h"
 
@@ -23,21 +22,26 @@
 namespace Poco {
 namespace MongoDB {
 
+ObjectId::ObjectId()
+{
+	memset(_id, 0, sizeof(_id));
+}
 
 ObjectId::ObjectId(const std::string& id)
 {
-	if (id.size() == 12)
-	{
-		std::string::const_iterator it = id.begin();
-		std::string::const_iterator end = id.end();
-		for (int i = 0; i < 12; ++it, ++i) _id[i] = *it;
-	}
-	else if (id.size())
-	{
-		throw Poco::InvalidArgumentException("ID must be 12 characters long.");
+	poco_assert_dbg(id.size() == 24);
+
+    const char *p = id.c_str();
+    for (std::size_t i = 0; i < 12; ++i) {
+		_id[i] = fromHex(p);
+		p += 2;
 	}
 }
 
+ObjectId::ObjectId(const ObjectId& copy)
+{
+	memcpy(_id, copy._id, sizeof(_id));
+}
 
 ObjectId::~ObjectId()
 {
diff --git a/MongoDB/testsuite/src/MongoDBTest.cpp b/MongoDB/testsuite/src/MongoDBTest.cpp
index 6ee5731d6..09024c75c 100644
--- a/MongoDB/testsuite/src/MongoDBTest.cpp
+++ b/MongoDB/testsuite/src/MongoDBTest.cpp
@@ -402,21 +402,7 @@ void MongoDBTest::testConnectionPool()
 
 void MongoDBTest::testObjectID()
 {
-	std::string str;
-	str.append(1, (char) 0x53);
-	str.append(1, (char) 0x6A);
-	str.append(1, (char) 0xEE);
-	str.append(1, (char) 0xBB);
-	str.append(1, (char) 0xA0);
-	str.append(1, (char) 0x81);
-	str.append(1, (char) 0xDE);
-	str.append(1, (char) 0x68);
-	str.append(1, (char) 0x15);
-	str.append(1, (char) 0x00);
-	str.append(1, (char) 0x00);
-	str.append(1, (char) 0x02);
-
-	ObjectId oid(str);
+	ObjectId oid("536aeebba081de6815000002");
 	std::string str2 = oid.toString();
 	assert(str2 == "536aeebba081de6815000002");
 }