diff --git a/src/libsodium/crypto_box/crypto_box_easy.c b/src/libsodium/crypto_box/crypto_box_easy.c
index c03c8ebf..ecc33b66 100644
--- a/src/libsodium/crypto_box/crypto_box_easy.c
+++ b/src/libsodium/crypto_box/crypto_box_easy.c
@@ -72,7 +72,7 @@ crypto_box_open_easy(unsigned char *m, const unsigned char *c,
     }
     memset(c_boxed, 0, crypto_box_BOXZEROBYTES);
     memcpy(c_boxed + crypto_box_BOXZEROBYTES, c, clen);
-    m_boxed_len = c_boxed_len + crypto_box_MACBYTES;
+    m_boxed_len = crypto_box_ZEROBYTES + (clen - crypto_box_MACBYTES);
     if ((m_boxed = (unsigned char *) malloc(m_boxed_len)) == NULL) {
         free(c_boxed);
         return -1;
diff --git a/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c b/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
index fd6508df..883fca88 100644
--- a/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
+++ b/src/libsodium/crypto_secretbox/crypto_secretbox_easy.c
@@ -74,7 +74,7 @@ crypto_secretbox_open_easy(unsigned char *m, const unsigned char *c,
     }
     memset(c_boxed, 0, crypto_secretbox_BOXZEROBYTES);
     memcpy(c_boxed + crypto_secretbox_BOXZEROBYTES, c, clen);
-    m_boxed_len = c_boxed_len + crypto_secretbox_MACBYTES;
+    m_boxed_len = crypto_secretbox_ZEROBYTES + (clen - crypto_secretbox_MACBYTES);
     if ((m_boxed = (unsigned char *) malloc(m_boxed_len)) == NULL) {
         free(c_boxed);
         return -1;