diff --git a/src/libsodium/crypto_core/salsa/ref/core_salsa_ref.c b/src/libsodium/crypto_core/salsa/ref/core_salsa_ref.c
index a077d7f4..c023378c 100644
--- a/src/libsodium/crypto_core/salsa/ref/core_salsa_ref.c
+++ b/src/libsodium/crypto_core/salsa/ref/core_salsa_ref.c
@@ -127,7 +127,7 @@ crypto_core_salsa20_constbytes(void)
 }
 
 #ifndef MINIMAL
-
+/* LCOV_EXCL_START */
 int
 crypto_core_salsa2012(unsigned char *out, const unsigned char *in,
                       const unsigned char *k, const unsigned char *c)
@@ -191,5 +191,5 @@ crypto_core_salsa208_constbytes(void)
 {
     return crypto_core_salsa208_CONSTBYTES;
 }
-
+/* LCOV_EXCL_END */
 #endif
diff --git a/src/libsodium/crypto_pwhash/argon2/argon2-core.c b/src/libsodium/crypto_pwhash/argon2/argon2-core.c
index bfe3fbbf..c4e4d842 100644
--- a/src/libsodium/crypto_pwhash/argon2/argon2-core.c
+++ b/src/libsodium/crypto_pwhash/argon2/argon2-core.c
@@ -113,9 +113,11 @@ allocate_memory(block_region **region, uint32_t m_cost)
     }
 #endif
     if (base == NULL) {
+        /* LCOV_EXCL_START */
         free(*region);
         *region = NULL;
-        return ARGON2_MEMORY_ALLOCATION_ERROR; /* LCOV_EXCL_LINE */
+        return ARGON2_MEMORY_ALLOCATION_ERROR;
+        /* LCOV_EXCL_STOP */
     }
     (*region)->base   = base;
     (*region)->memory = memory;
diff --git a/src/libsodium/sodium/runtime.c b/src/libsodium/sodium/runtime.c
index a5a89bca..9dfe54f8 100644
--- a/src/libsodium/sodium/runtime.c
+++ b/src/libsodium/sodium/runtime.c
@@ -203,11 +203,13 @@ _sodium_runtime_intel_cpu_features(CPUFeatures * const cpu_features)
         unsigned int cpu_info7[4];
 
         _cpuid(cpu_info7, 0x00000007);
+        /* LCOV_EXCL_START */
         if ((cpu_info7[1] & CPUID_EBX_AVX512F) == CPUID_EBX_AVX512F &&
             (xcr0 & (XCR0_OPMASK | XCR0_ZMM_HI256 | XCR0_HI16_ZMM))
             == (XCR0_OPMASK | XCR0_ZMM_HI256 | XCR0_HI16_ZMM)) {
             cpu_features->has_avx512f = 1;
         }
+        /* LCOV_EXCL_STOP */
     }
 #endif
 
diff --git a/test/default/box_seal.c b/test/default/box_seal.c
index f9c970bc..e19ddd62 100644
--- a/test/default/box_seal.c
+++ b/test/default/box_seal.c
@@ -2,8 +2,8 @@
 #define TEST_NAME "box_seal"
 #include "cmptest.h"
 
-int
-main(void)
+static
+void tv1(void)
 {
     unsigned char  pk[crypto_box_PUBLICKEYBYTES];
     unsigned char  sk[crypto_box_SECRETKEYBYTES];
@@ -22,11 +22,11 @@ main(void)
     randombytes_buf(m, m_len);
     if (crypto_box_seal(c, m, m_len, pk) != 0) {
         printf("crypto_box_seal() failure\n");
-        return 1;
+        return;
     }
     if (crypto_box_seal_open(m2, c, c_len, pk, sk) != 0) {
         printf("crypto_box_seal_open() failure\n");
-        return 1;
+        return;
     }
     printf("%d\n", memcmp(m, m2, m_len));
 
@@ -39,6 +39,56 @@ main(void)
     sodium_free(m2);
 
     assert(crypto_box_sealbytes() == crypto_box_SEALBYTES);
+}
 
+#ifndef SODIUM_LIBRARY_MINIMAL
+static
+void tv2(void)
+{
+    unsigned char  pk[crypto_box_curve25519xchacha20poly1305_PUBLICKEYBYTES];
+    unsigned char  sk[crypto_box_curve25519xchacha20poly1305_SECRETKEYBYTES];
+    unsigned char *c;
+    unsigned char *m;
+    unsigned char *m2;
+    size_t         m_len;
+    size_t         c_len;
+
+    crypto_box_curve25519xchacha20poly1305_keypair(pk, sk);
+    m_len = (size_t) randombytes_uniform(1000);
+    c_len = crypto_box_curve25519xchacha20poly1305_SEALBYTES + m_len;
+    m     = (unsigned char *) sodium_malloc(m_len);
+    m2    = (unsigned char *) sodium_malloc(m_len);
+    c     = (unsigned char *) sodium_malloc(c_len);
+    randombytes_buf(m, m_len);
+    if (crypto_box_curve25519xchacha20poly1305_seal(c, m, m_len, pk) != 0) {
+        printf("crypto_box_curve25519xchacha20poly1305_seal() failure\n");
+        return;
+    }
+    if (crypto_box_curve25519xchacha20poly1305_seal_open(m2, c, c_len, pk, sk) != 0) {
+        printf("crypto_box_curve25519xchacha20poly1305_seal_open() failure\n");
+        return;
+    }
+    printf("%d\n", memcmp(m, m2, m_len));
+
+    printf("%d\n", crypto_box_curve25519xchacha20poly1305_seal_open(m, c, 0U, pk, sk));
+    printf("%d\n", crypto_box_curve25519xchacha20poly1305_seal_open(m, c, c_len - 1U, pk, sk));
+    printf("%d\n", crypto_box_curve25519xchacha20poly1305_seal_open(m, c, c_len, sk, pk));
+
+    sodium_free(c);
+    sodium_free(m);
+    sodium_free(m2);
+
+    assert(crypto_box_curve25519xchacha20poly1305_sealbytes() ==
+           crypto_box_curve25519xchacha20poly1305_SEALBYTES);
+}
+#endif
+
+int
+main(void)
+{
+    tv1();
+#ifndef SODIUM_LIBRARY_MINIMAL
+    tv2();
+#endif
     return 0;
 }
diff --git a/test/default/box_seal.exp b/test/default/box_seal.exp
index 78ea705a..ded7a43c 100644
--- a/test/default/box_seal.exp
+++ b/test/default/box_seal.exp
@@ -2,3 +2,7 @@
 -1
 -1
 -1
+0
+-1
+-1
+-1