diff --git a/doc/security-warnings.md b/doc/security-warnings.md
index 9838154c6..fcf476409 100644
--- a/doc/security-warnings.md
+++ b/doc/security-warnings.md
@@ -7,6 +7,14 @@ Security Audit
 Zcash has not yet been subjected to a formal third-party security review. This
 section will be updated with links to security audit reports in the future.
 
+x86-64 Linux Only
+-----------------------
+
+There are [known bugs](https://github.com/scipr-lab/libsnark/issues/26) which
+make proving keys generated on 64-bit systems unusable on 32-bit and big-endian
+systems. It's unclear if a warning will be issued in this case, or if the
+proving system will be silently compromised.
+
 Side-Channel Attacks
 --------------------