diff --git a/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c b/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
index e2ba6234..d3754883 100644
--- a/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
+++ b/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
@@ -99,6 +99,8 @@ crypto_secretbox_open_detached(unsigned char *m, const unsigned char *c,
         return -1;
     }
     if (m == NULL) {
+        sodium_memzero(subkey, sizeof subkey);
+        sodium_memzero(block0, sizeof block0);
         return 0;
     }
     ACQUIRE_FENCE;
diff --git a/src/libsodium/crypto_secretbox/xchacha20poly1305/secretbox_xchacha20poly1305.c b/src/libsodium/crypto_secretbox/xchacha20poly1305/secretbox_xchacha20poly1305.c
index aa1b5b4b..484a129f 100644
--- a/src/libsodium/crypto_secretbox/xchacha20poly1305/secretbox_xchacha20poly1305.c
+++ b/src/libsodium/crypto_secretbox/xchacha20poly1305/secretbox_xchacha20poly1305.c
@@ -106,6 +106,8 @@ crypto_secretbox_xchacha20poly1305_open_detached(unsigned char *m,
         return -1;
     }
     if (m == NULL) {
+        sodium_memzero(subkey, sizeof subkey);
+        sodium_memzero(block0, sizeof block0);
         return 0;
     }
     ACQUIRE_FENCE;