diff --git a/src/libsodium/include/sodium/private/ed25519_ref10.h b/src/libsodium/include/sodium/private/ed25519_ref10.h
index d309e021..5f7e67e3 100644
--- a/src/libsodium/include/sodium/private/ed25519_ref10.h
+++ b/src/libsodium/include/sodium/private/ed25519_ref10.h
@@ -129,6 +129,9 @@ void sc25519_invert(unsigned char recip[32], const unsigned char s[32]);
 
 void sc25519_reduce(unsigned char s[64]);
 
+void sc25519_mul(unsigned char s[32], const unsigned char a[32],
+                 const unsigned char b[32]);
+
 void sc25519_muladd(unsigned char s[32], const unsigned char a[32],
                     const unsigned char b[32], const unsigned char c[32]);