diff --git a/des.cpp b/des.cpp
index 3afe0b31..af9308c1 100644
--- a/des.cpp
+++ b/des.cpp
@@ -424,15 +424,18 @@ void DES_XEX3::Base::UncheckedSetKey(CipherDir dir, const byte *key, unsigned in
 {
 	AssertValidKeyLength(length);
 
+	if (!m_des.get())
+		m_des.reset(new DES::Encryption);
+
 	memcpy(m_x1, key+(dir==ENCRYPTION?0:2*8), BLOCKSIZE);
-	m_des.UncheckedSetKey(dir, key+8);
+	m_des->UncheckedSetKey(dir, key+8);
 	memcpy(m_x3, key+(dir==DECRYPTION?0:2*8), BLOCKSIZE);
 }
 
 void DES_XEX3::Base::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
 {
 	xorbuf(outBlock, inBlock, m_x1, BLOCKSIZE);
-	m_des.ProcessAndXorBlock(outBlock, xorBlock, outBlock);
+	m_des->ProcessAndXorBlock(outBlock, xorBlock, outBlock);
 	xorbuf(outBlock, m_x3, BLOCKSIZE);
 }
 
diff --git a/des.h b/des.h
index 272bc53e..8400fa1b 100644
--- a/des.h
+++ b/des.h
@@ -116,7 +116,9 @@ class DES_XEX3 : public DES_XEX3_Info, public BlockCipherDocumentation
 
 	protected:
 		FixedSizeSecBlock<byte, BLOCKSIZE> m_x1, m_x3;
-		DES::Encryption m_des;
+		// VS2005 workaround: calling modules compiled with /clr gets unresolved external symbol DES::Base::ProcessAndXorBlock
+		// if we use DES::Encryption here directly without value_ptr.
+		value_ptr<DES::Encryption> m_des;
 	};
 
 public: