Try exporting one of the functions used in another module
diff --git a/OpenSSL/crypto/x509.c b/OpenSSL/crypto/x509.c
index 9c2448c..144a6fa 100644
--- a/OpenSSL/crypto/x509.c
+++ b/OpenSSL/crypto/x509.c
@@ -727,6 +727,7 @@
  *                      free the "real" X509 object
  * Returns:   The newly created X509 object
  */
+__declspec(dllexport)
 crypto_X509Obj *
 crypto_X509_New(X509 *cert, int dealloc)
 {