diff --git a/src/libsodium/crypto_onetimeauth/poly1305/sse2/poly1305_sse2.c b/src/libsodium/crypto_onetimeauth/poly1305/sse2/poly1305_sse2.c
index 6899589d..3a9fe51b 100644
--- a/src/libsodium/crypto_onetimeauth/poly1305/sse2/poly1305_sse2.c
+++ b/src/libsodium/crypto_onetimeauth/poly1305/sse2/poly1305_sse2.c
@@ -606,6 +606,8 @@ poly1305_finish_ext(poly1305_state_internal_t *st, const unsigned char *m,
 
     *(uint64_t *)(mac + 0) = h0;
     *(uint64_t *)(mac + 8) = h1;
+
+    sodium_memzero((void *)st, sizeof *st);
 }
 
 static void