diff --git a/common/tests/advio.cpp b/common/tests/advio.cpp
index f0364c765..9d1458973 100644
--- a/common/tests/advio.cpp
+++ b/common/tests/advio.cpp
@@ -53,7 +53,7 @@ Test(advio, local)
 {
 	AFILE *af;
 	int ret;
-	char *buf = NULL;
+	char *buf = nullptr;
 	size_t buflen = 0;
 
 	/* We open this file and check the first line */
@@ -119,7 +119,7 @@ Test(advio, resume)
 	AFILE *af1, *af2;
 	char *fn, dir[] = "/tmp/temp.XXXXXX";
 	char line1[32];
-	char *line2 = NULL;
+	char *line2 = nullptr;
 	size_t linelen = 0;
 
 	retp = mkdtemp(dir);
diff --git a/common/tests/hash_table.cpp b/common/tests/hash_table.cpp
index c83939d43..0d163b12c 100644
--- a/common/tests/hash_table.cpp
+++ b/common/tests/hash_table.cpp
@@ -69,6 +69,6 @@ Test(hash_table, hash_table_lookup)
 	ret = hash_table_insert(&ht, keys[0], (void *) values[0]);
 	cr_assert(!ret);
 
-	ret = hash_table_destroy(&ht, NULL, false);
+	ret = hash_table_destroy(&ht, nullptr, false);
 	cr_assert(!ret);
 }
diff --git a/common/tests/json_buffer.cpp b/common/tests/json_buffer.cpp
index c7d54147b..a24b1fc2a 100644
--- a/common/tests/json_buffer.cpp
+++ b/common/tests/json_buffer.cpp
@@ -45,7 +45,7 @@ Test(json_buffer, decode)
 
 	buf.insert(buf.begin(), e, e+len);
 
-	k = json_loads(e, 0, NULL);
+	k = json_loads(e, 0, nullptr);
 	cr_assert_not_null(k);
 
 	j = buf.decode();
@@ -61,7 +61,7 @@ Test(json_buffer, encode)
 
 	const char *e = "{\"id\": \"5a786626-fbc6-4c04-98c2-48027e68c2fa\"}";
 
-	k = json_loads(e, 0, NULL);
+	k = json_loads(e, 0, nullptr);
 	cr_assert_not_null(k);
 
 	ret = buf.encode(k);
@@ -84,7 +84,7 @@ Test(json_buffer, encode_decode)
 
 	const char *e = "{\"id\": \"5a786626-fbc6-4c04-98c2-48027e68c2fa\"}";
 
-	k = json_loads(e, 0, NULL);
+	k = json_loads(e, 0, nullptr);
 	cr_assert_not_null(k);
 
 	ret = buf.encode(k);
diff --git a/common/tests/list.cpp b/common/tests/list.cpp
index 97c2a0717..5e430ccc0 100644
--- a/common/tests/list.cpp
+++ b/common/tests/list.cpp
@@ -56,7 +56,7 @@ Test(list, list_lookup)
 
 	cr_assert_eq(found->data, 13);
 
-	list_destroy(&l, NULL, true);
+	list_destroy(&l, nullptr, true);
 }
 
 Test(list, list_search)
@@ -84,7 +84,7 @@ Test(list, list_search)
 	char *not_found = (char *) list_search(&l, (cmp_cb_t) strcmp, negative);
 	cr_assert_null(not_found);
 
-	list_destroy(&l, NULL, false);
+	list_destroy(&l, nullptr, false);
 }
 
 struct content {
@@ -137,7 +137,7 @@ Test(list, basics)
 		list_push(&l, (void *) i);
 	}
 
-	cr_assert_eq(list_at_safe(&l, 555), NULL);
+	cr_assert_eq(list_at_safe(&l, 555), nullptr);
 	cr_assert_eq(list_last(&l), (void *) 99);
 	cr_assert_eq(list_first(&l), (void *) 0);
 
@@ -164,7 +164,7 @@ Test(list, basics)
 	ret = list_contains(&l, (void *) 55);
 	cr_assert(!ret);
 
-	list_destroy(&l, NULL, false);
+	list_destroy(&l, nullptr, false);
 
 	ret = list_length(&l);
 	cr_assert_eq(ret, -1, "List not properly destroyed: l.length = %zd", l.length);
diff --git a/common/tests/utils.cpp b/common/tests/utils.cpp
index d7a09708a..dca95246d 100644
--- a/common/tests/utils.cpp
+++ b/common/tests/utils.cpp
@@ -134,7 +134,7 @@ Test(utils, is_pow2)
 
 Test(utils, strf)
 {
-	char *buf = NULL;
+	char *buf = nullptr;
 
 	buf = strcatf(&buf, "Hallo %s", "Steffen.");
 	cr_assert_str_eq(buf, "Hallo Steffen.");