diff --git a/changes/bug40078 b/changes/bug40078
new file mode 100644
index 0000000000..717309e076
--- /dev/null
+++ b/changes/bug40078
@@ -0,0 +1,3 @@
+  o Minor bugfix (crypto):
+    - Disable the unused batch verification feature of ed25519-donna. Fixes
+      bug 40078; bugfix on 0.2.6.1-alpha. Found by Henry de Valence.
\ No newline at end of file
diff --git a/src/lib/crypt_ops/crypto_ed25519.c b/src/lib/crypt_ops/crypto_ed25519.c
index e2b181d2a8..1f02b86880 100644
--- a/src/lib/crypt_ops/crypto_ed25519.c
+++ b/src/lib/crypt_ops/crypto_ed25519.c
@@ -102,7 +102,7 @@ static const ed25519_impl_t impl_donna = {
 
   ed25519_donna_open,
   ed25519_donna_sign,
-  ed25519_sign_open_batch_donna,
+  NULL, /* Don't use donna's batching code because of #40078 */
 
   ed25519_donna_blind_secret_key,
   ed25519_donna_blind_public_key,