diff --git a/examples/dbcrypt/CryptKeyHolder.cpp b/examples/dbcrypt/CryptKeyHolder.cpp
index 3e52963d6f..3b7f5ec60f 100644
--- a/examples/dbcrypt/CryptKeyHolder.cpp
+++ b/examples/dbcrypt/CryptKeyHolder.cpp
@@ -138,7 +138,7 @@ private:
 			: holder(p)
 		{ }
 
-		unsigned int callback(unsigned int, const void*, unsigned int length, void* buffer)
+		unsigned int callback(unsigned int, const void*, unsigned int length, void* buffer) override
 		{
 			ISC_UCHAR k = holder->getKey();
 			if (!k)