diff --git a/ChangeLog b/ChangeLog
index d13c50727b0dd23b7b29d9258c2b6c873ffd4166..c385ac062fa7e1d9cbe20eccb88d1925c5789307 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 2019-07-08  Niels Möller  <nisse@lysator.liu.se>
 
+	* nettle-types.h (union nettle_block16): Mark w member as deprecated.
 	* eax.c (block16_xor): Use uint64_t member of nettle_block16.
 	* gcm.c (gcm_gf_add, gcm_gf_shift, gcm_gf_shift_8): Likewise.
 
diff --git a/nettle-types.h b/nettle-types.h
index 87292ac697305d0b57c3b6fc252366f9540b8a8b..4fc0ae5e87d67ffda399c43c172c5edf70c54797 100644
--- a/nettle-types.h
+++ b/nettle-types.h
@@ -61,7 +61,7 @@ extern "C" {
 union nettle_block16
 {
   uint8_t b[16];
-  unsigned long w[16 / sizeof(unsigned long)];
+  unsigned long w[16 / sizeof(unsigned long)] _NETTLE_ATTRIBUTE_DEPRECATED;
   uint64_t u64[2];
 };