diff --git a/test/default/auth.c b/test/default/auth.c
index 1f4553ca..23ac9277 100644
--- a/test/default/auth.c
+++ b/test/default/auth.c
@@ -67,7 +67,7 @@ main(void)
             printf("\n");
     }
 
-    // Empty message tests: HMAC-SHA512
+    /* Empty message tests: HMAC-SHA512 */
     memset(a2, 0, sizeof a2);
     crypto_auth_hmacsha512_init(&st, key, sizeof key);
     crypto_auth_hmacsha512_final(&st, a2);
@@ -80,11 +80,11 @@ main(void)
 
     memset(a3, 0, sizeof a3);
     crypto_auth_hmacsha512_init(&st, key, sizeof key);
-    crypto_auth_hmacsha512_update(&st, NULL, 0U);
+    crypto_auth_hmacsha512_update(&st, guard_page, 0U);
     crypto_auth_hmacsha512_final(&st, a3);
     assert(sodium_memcmp(a2, a3, sizeof a2) == 0);
 
-    // Empty message tests: HMAC-SHA512-256
+    /* Empty message tests: HMAC-SHA512-256 */
     memset(a2, 0, sizeof a2);
     crypto_auth_hmacsha512256_init(&st512_256, key, sizeof key);
     crypto_auth_hmacsha512256_final(&st512_256, a2);
@@ -97,12 +97,12 @@ main(void)
 
     memset(a3, 0, sizeof a3);
     crypto_auth_hmacsha512256_init(&st512_256, key, sizeof key);
-    crypto_auth_hmacsha512256_update(&st512_256, NULL, 0U);
+    crypto_auth_hmacsha512256_update(&st512_256, guard_page, 0U);
     crypto_auth_hmacsha512256_final(&st512_256, a3);
     assert(sodium_memcmp(a2, a3, sizeof a2) == 0);
 
+    /* Empty message tests: HMAC-SHA256 */
 
-    // Empty message tests: HMAC-SHA256
     memset(a2, 0, sizeof a2);
     crypto_auth_hmacsha256_init(&st256, key, sizeof key);
     crypto_auth_hmacsha256_final(&st256, a2);
@@ -115,10 +115,12 @@ main(void)
 
     memset(a3, 0, sizeof a3);
     crypto_auth_hmacsha256_init(&st256, key, sizeof key);
-    crypto_auth_hmacsha256_update(&st256, NULL, 0U);
+    crypto_auth_hmacsha256_update(&st256, guard_page, 0U);
     crypto_auth_hmacsha256_final(&st256, a3);
     assert(sodium_memcmp(a2, a3, sizeof a2) == 0);
 
+    /* --- */
+
     assert(crypto_auth_bytes() > 0U);
     assert(crypto_auth_keybytes() > 0U);
     assert(strcmp(crypto_auth_primitive(), "hmacsha512256") == 0);
diff --git a/test/default/auth3.c b/test/default/auth3.c
index 786f6f2e..ca90aa7b 100644
--- a/test/default/auth3.c
+++ b/test/default/auth3.c
@@ -29,9 +29,8 @@ main(void)
 
     printf("%d\n", crypto_auth_hmacsha256_verify(a, c, sizeof c, key));
 
-    // Test empty message with NULL pointer
-    crypto_auth_hmacsha256(a2, NULL, 0U, key);
-    assert(crypto_auth_hmacsha256_verify(a2, NULL, 0U, key) == 0);
+    crypto_auth_hmacsha256(a2, guard_page, 0U, key);
+    assert(crypto_auth_hmacsha256_verify(a2, guard_page, 0U, key) == 0);
 
     return 0;
 }
diff --git a/test/default/auth5.c b/test/default/auth5.c
index 5559ac51..955c9cfb 100644
--- a/test/default/auth5.c
+++ b/test/default/auth5.c
@@ -33,10 +33,9 @@ main(void)
         }
     }
 
-    // Test empty message with NULL pointer
     crypto_auth_keygen(key);
-    crypto_auth(a, NULL, 0U, key);
-    assert(crypto_auth_verify(a, NULL, 0U, key) == 0);
+    crypto_auth(a, guard_page, 0U, key);
+    assert(crypto_auth_verify(a, guard_page, 0U, key) == 0);
 
     return 0;
 }
diff --git a/test/default/auth7.c b/test/default/auth7.c
index 71f97dff..3d087f8e 100644
--- a/test/default/auth7.c
+++ b/test/default/auth7.c
@@ -33,10 +33,9 @@ main(void)
         }
     }
 
-    // Test empty message with NULL pointer
     crypto_auth_keygen(key);
-    crypto_auth_hmacsha512(a, NULL, 0U, key);
-    assert(crypto_auth_hmacsha512_verify(a, NULL, 0U, key) == 0);
+    crypto_auth_hmacsha512(a, guard_page, 0U, key);
+    assert(crypto_auth_hmacsha512_verify(a, guard_page, 0U, key) == 0);
 
     return 0;
 }
diff --git a/test/default/box_easy.c b/test/default/box_easy.c
index b7d0a028..2e6a20f9 100644
--- a/test/default/box_easy.c
+++ b/test/default/box_easy.c
@@ -50,7 +50,7 @@ main(void)
 
     /* Null message */
 
-    ret = crypto_box_easy(c, NULL, 0, nonce, bobpk, alicesk);
+    ret = crypto_box_easy(c, guard_page, 0, nonce, bobpk, alicesk);
     assert(ret == 0);
     for (i = 0; i < 1 + crypto_box_MACBYTES; ++i) {
         printf(",0x%02x", (unsigned int) c[i]);
diff --git a/test/default/cmptest.h b/test/default/cmptest.h
index 4625d551..1ecc5cd9 100644
--- a/test/default/cmptest.h
+++ b/test/default/cmptest.h
@@ -178,11 +178,15 @@ int main(void)
     if (sodium_init() != 0) {
         return 99;
     }
+# if defined(__EMSCRIPTEN__) || defined(__SANITIZE_ADDRESS__)
+    guard_page = _guard_page = NULL;
+#else
     if ((_guard_page = (unsigned char *) sodium_malloc(0)) == NULL) {
         perror("sodium_malloc()");
         return 99;
     }
     guard_page = _guard_page + 1;
+#endif
     if (xmain() != 0) {
         return 99;
     }
diff --git a/test/default/codecs.c b/test/default/codecs.c
index 0ca7a49b..726c96bc 100644
--- a/test/default/codecs.c
+++ b/test/default/codecs.c
@@ -20,10 +20,10 @@ main(void)
     printf("%s\n",
            sodium_bin2hex(buf3, 33U, (const unsigned char *) "0123456789ABCDEF",
                           16U));
-    printf("bin2hex(..., NULL, 0):%s\n",
-           sodium_bin2hex(buf4, sizeof(buf4), NULL, 0U));
+    printf("bin2hex(..., guard_page, 0):%s\n",
+           sodium_bin2hex(buf3, sizeof buf3, guard_page, 0U));
     printf("bin2hex(..., \"\", 0):%s\n",
-           sodium_bin2hex(buf4, sizeof(buf4), (const unsigned char *) "", 0U));
+           sodium_bin2hex(buf3, sizeof buf3, (const unsigned char *) "", 0U));
 
     hex = "Cafe : 6942";
     sodium_hex2bin(buf4, sizeof buf4, hex, strlen(hex), ": ", &bin_len,
@@ -84,10 +84,11 @@ main(void)
         printf("sodium_hex2bin() with an extra character and no end pointer\n");
     }
 
-    assert(sodium_hex2bin(buf4, sizeof(buf4), NULL, 0U, NULL, &bin_len, NULL) == 0);
+    assert(sodium_hex2bin(buf4, sizeof buf4, (const char *) guard_page, 0U,
+                          NULL, &bin_len, NULL) == 0);
     assert(bin_len == 0);
 
-    assert(sodium_hex2bin(buf4, sizeof(buf4), "", 0U, NULL, &bin_len, NULL) == 0);
+    assert(sodium_hex2bin(buf4, sizeof buf4, "", 0U, NULL, &bin_len, NULL) == 0);
     assert(bin_len == 0);
 
     printf("%s\n",
@@ -105,9 +106,6 @@ main(void)
     printf("%s\n",
            sodium_bin2base64(buf3, 1U, guard_page,
                              0U, sodium_base64_VARIANT_ORIGINAL));
-    printf("%s\n",
-           sodium_bin2base64(buf3, 1U, NULL,
-                             0U, sodium_base64_VARIANT_ORIGINAL));
     printf("%s\n",
            sodium_bin2base64(buf3, 5U, (const unsigned char *) "a",
                              1U, sodium_base64_VARIANT_ORIGINAL));
@@ -215,10 +213,11 @@ main(void)
     assert(sodium_base642bin(buf1, sizeof buf1, "ka*w*=*", (size_t) 7U, "*~", NULL, NULL,
                              sodium_base64_VARIANT_ORIGINAL) == 0);
 
-    assert(sodium_base642bin(buf1, sizeof buf1, "", 0U, NULL, &bin_len, NULL,
-                             sodium_base64_VARIANT_ORIGINAL) == 0);
+    assert(sodium_base642bin(buf1, sizeof buf1, (const char *) guard_page, 0U,
+                             NULL, &bin_len, NULL, sodium_base64_VARIANT_ORIGINAL) == 0);
     assert(bin_len == 0);
-    assert(sodium_base642bin(buf1, sizeof buf1, NULL, 0U, NULL, &bin_len, NULL,
+
+    assert(sodium_base642bin(buf1, sizeof buf1, "", 0U, NULL, &bin_len, NULL,
                              sodium_base64_VARIANT_ORIGINAL) == 0);
     assert(bin_len == 0);
 
diff --git a/test/default/codecs.exp b/test/default/codecs.exp
index 748b1a18..171834ed 100644
--- a/test/default/codecs.exp
+++ b/test/default/codecs.exp
@@ -1,5 +1,5 @@
 30313233343536373839414243444546
-bin2hex(..., NULL, 0):
+bin2hex(..., guard_page, 0):
 bin2hex(..., "", 0):
 4:cafe6942
 dt1: 11
@@ -14,7 +14,6 @@ dt6: 11
 -_DxMDEyMzQ1Njc4OUFCQ0RFRmFi
 -_DxMDEyMzQ1Njc4OUFCQ0RFRmFiYw
 
-
 YQ==
 YWI=
 YWJj
diff --git a/test/default/sodium_utils.c b/test/default/sodium_utils.c
index 8bd8509c..844e16cf 100644
--- a/test/default/sodium_utils.c
+++ b/test/default/sodium_utils.c
@@ -29,10 +29,10 @@ main(void)
     printf("%d\n", sodium_memcmp(buf1, buf2, 0U));
     sodium_memzero(buf2, sizeof buf2 / 2);
     printf("%d\n", sodium_memcmp(buf1, buf2, sizeof buf1));
-    printf("%d\n", sodium_memcmp(buf1, NULL, 0U));
-    printf("%d\n", sodium_memcmp(NULL, buf2, 0U));
-    printf("%d\n", sodium_memcmp(NULL, NULL, 0U));
-    sodium_memzero(NULL, 0U);
+    printf("%d\n", sodium_memcmp(buf1, guard_page, 0U));
+    printf("%d\n", sodium_memcmp(guard_page, buf2, 0U));
+    printf("%d\n", sodium_memcmp(guard_page, guard_page, 0U));
+    sodium_memzero(guard_page, 0U);
 
     memset(nonce, 0, sizeof nonce);
     sodium_increment(nonce, sizeof nonce);
@@ -163,18 +163,18 @@ main(void)
     sodium_add(nonce, nonce, 0U);
     printf("%s\n",
            sodium_bin2hex(nonce_hex, sizeof nonce_hex, nonce, sizeof nonce));
-    sodium_add(nonce, NULL, 0U);
+    sodium_add(nonce, guard_page, 0U);
     printf("%s\n",
            sodium_bin2hex(nonce_hex, sizeof nonce_hex, nonce, sizeof nonce));
-    sodium_add(NULL, nonce, 0U);
+    sodium_add(guard_page, nonce, 0U);
 
     sodium_sub(nonce, nonce, 0U);
     printf("%s\n",
            sodium_bin2hex(nonce_hex, sizeof nonce_hex, nonce, sizeof nonce));
-    sodium_sub(nonce, NULL, 0U);
+    sodium_sub(nonce, guard_page, 0U);
     printf("%s\n",
            sodium_bin2hex(nonce_hex, sizeof nonce_hex, nonce, sizeof nonce));
-    sodium_sub(NULL, nonce, 0U);
+    sodium_sub(guard_page, nonce, 0U);
 
     randombytes_buf(buf1, 64U);
     randombytes_buf(buf2, 64U);