diff --git a/ChangeLog b/ChangeLog
index bfaa5e963000ff94a7e64df213055cb5cfbc9bdd..4ec5b49a5e2739a3754822bb2115af393314a43e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2022-02-18  Niels Möller  <nisse@lysator.liu.se>
+
+	* block-internal.h (block16_zero): New function.
+
 2022-02-17  Niels Möller  <nisse@lysator.liu.se>
 
 	* gcm.c: Require that GCM_TABLE_BITS == 8. Delete old code for
diff --git a/block-internal.h b/block-internal.h
index 88e19be333c8f1372adc10b649595f5380af1d35..d7b0c3150cc466dd0c549a887f93b6d7579ffe74 100644
--- a/block-internal.h
+++ b/block-internal.h
@@ -42,6 +42,13 @@
 #include "nettle-types.h"
 #include "memxor.h"
 
+static inline void
+block16_zero (union nettle_block16 *r)
+{
+  static const union nettle_block16 zero_block;
+  *r = zero_block;
+}
+
 static inline void
 block16_xor (union nettle_block16 *r,
 	     const union nettle_block16 *x)