diff --git a/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c b/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
index fd48710f..25af3a92 100644
--- a/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
+++ b/src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
@@ -50,6 +50,9 @@ load_4(const unsigned char *in)
 # include "fe_25_5/fe.h"
 #endif
 
+/*
+ * Inversion - returns 0 if z=0
+ */
 void
 fe25519_invert(fe25519 out, const fe25519 z)
 {