diff --git a/Crypto/src/ECDSADigestEngine.cpp b/Crypto/src/ECDSADigestEngine.cpp
index b69addaee..ac85a9b75 100644
--- a/Crypto/src/ECDSADigestEngine.cpp
+++ b/Crypto/src/ECDSADigestEngine.cpp
@@ -16,6 +16,7 @@
 #include "Poco/Crypto/ECDSADigestEngine.h"
 #include "Poco/Crypto/CryptoException.h"
 #include <openssl/ecdsa.h>
+#include <openssl/bn.h>
 
 
 namespace Poco {