diff --git a/ChangeLog b/ChangeLog
index 92658fe7cd1c6842fd2873d0f93e90166c98fb0d..5975cab875c606766110f22a23bce98d581085aa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,8 @@
 
 2018-01-08  Niels Möller  <nisse@lysator.liu.se>
 
+	* nettle-types.h (union nettle_block16): Add uint64_t field.
+
 	* configure.ac: Check for __builtin_bswap64, define
 	HAVE_BUILTIN_BSWAP64 if available.
 
diff --git a/nettle-types.h b/nettle-types.h
index 84c375d2e6d49608fe7c5cecb0412d04228c0eca..f04655d6582988d3eecaeb5f56a44e9bafa27806 100644
--- a/nettle-types.h
+++ b/nettle-types.h
@@ -48,6 +48,7 @@ union nettle_block16
 {
   uint8_t b[16];
   unsigned long w[16 / sizeof(unsigned long)];
+  uint64_t u64[2];
 };
 
 /* Randomness. Used by key generation and dsa signature creation. */