diff --git a/source/tests/metacall_distributable_test/source/metacall_distributable_test.cpp b/source/tests/metacall_distributable_test/source/metacall_distributable_test.cpp
index c701dc880..1d91f4027 100644
--- a/source/tests/metacall_distributable_test/source/metacall_distributable_test.cpp
+++ b/source/tests/metacall_distributable_test/source/metacall_distributable_test.cpp
@@ -133,7 +133,13 @@ TEST_F(metacall_distributable_test, DefaultConstructor)
 
 		metacall_value_destroy(ret);
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("say_null"));
+		ret = metacall("say_null");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("say_hello", "meta-programmer");
 
diff --git a/source/tests/metacall_ducktype_test/source/metacall_ducktype_test.cpp b/source/tests/metacall_ducktype_test/source/metacall_ducktype_test.cpp
index 3c18cd1b2..1fe77a775 100644
--- a/source/tests/metacall_ducktype_test/source/metacall_ducktype_test.cpp
+++ b/source/tests/metacall_ducktype_test/source/metacall_ducktype_test.cpp
@@ -249,7 +249,13 @@ TEST_F(metacall_ducktype_test, DefaultConstructor)
 			METACALL_INVALID
 		};
 
-		EXPECT_EQ((void *) NULL, (void *) metacallt("say_null", say_null_invalid_ids));
+		ret = metacallt("say_null", say_null_invalid_ids);
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		const enum metacall_value_id say_hello_str_ids[] =
 		{
diff --git a/source/tests/metacall_load_configuration_test/source/metacall_load_configuration_test.cpp b/source/tests/metacall_load_configuration_test/source/metacall_load_configuration_test.cpp
index 16d1f5357..9f5879a72 100644
--- a/source/tests/metacall_load_configuration_test/source/metacall_load_configuration_test.cpp
+++ b/source/tests/metacall_load_configuration_test/source/metacall_load_configuration_test.cpp
@@ -215,7 +215,13 @@ TEST_F(metacall_load_configuration_test, DefaultConstructor)
 
 		metacall_value_destroy(ret);
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("say_null"));
+		ret = metacall("say_null");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("say_hello", "meta-programmer");
 
diff --git a/source/tests/metacall_test/source/metacall_test.cpp b/source/tests/metacall_test/source/metacall_test.cpp
index 8775d94bb..e4e59a78b 100644
--- a/source/tests/metacall_test/source/metacall_test.cpp
+++ b/source/tests/metacall_test/source/metacall_test.cpp
@@ -300,7 +300,13 @@ TEST_F(metacall_test, DefaultConstructor)
 
 		metacall_value_destroy(ret);
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("say_null"));
+		ret = metacall("say_null");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("say_hello", "meta-programmer");
 
diff --git a/source/tests/metacall_test/source/metacall_test_split.cpp b/source/tests/metacall_test/source/metacall_test_split.cpp
index 855b64a73..792ab0e71 100644
--- a/source/tests/metacall_test/source/metacall_test_split.cpp
+++ b/source/tests/metacall_test/source/metacall_test_split.cpp
@@ -155,7 +155,13 @@ class metacall_loader_test : public testing::Test
 
 		value_destroy(ret);
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("say_null"));
+		ret = metacall("say_null");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("say_hello", "meta-programmer");
 
diff --git a/source/tests/py_loader_port_test/source/py_loader_port_test.cpp b/source/tests/py_loader_port_test/source/py_loader_port_test.cpp
index 2db1e2ea8..c14633b96 100644
--- a/source/tests/py_loader_port_test/source/py_loader_port_test.cpp
+++ b/source/tests/py_loader_port_test/source/py_loader_port_test.cpp
@@ -75,7 +75,13 @@ TEST_F(py_loader_port_test, DefaultConstructor)
 
 		metacall_value_destroy(ret);
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("say_null"));
+		ret = metacall("say_null");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("say_hello", "meta-programmer");
 
diff --git a/source/tests/rb_loader_parser_integration_test/source/rb_loader_parser_integration_test.cpp b/source/tests/rb_loader_parser_integration_test/source/rb_loader_parser_integration_test.cpp
index 2c81f8056..d403f9038 100644
--- a/source/tests/rb_loader_parser_integration_test/source/rb_loader_parser_integration_test.cpp
+++ b/source/tests/rb_loader_parser_integration_test/source/rb_loader_parser_integration_test.cpp
@@ -49,9 +49,21 @@ TEST_F(rb_loader_parser_integration_test, DefaultConstructor)
 
 		EXPECT_EQ((int) 0, (int) metacall_load_from_file("rb", rb_scripts, sizeof(rb_scripts) / sizeof(rb_scripts[0]), NULL));
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("cache_initialize"));
+		ret = metacall("cache_initialize");
 
-		EXPECT_EQ((void *) NULL, (void *) metacall("cache_set", "meta", "call"));
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
+
+		ret = metacall("cache_set", "meta", "call");
+
+		EXPECT_NE((void *) NULL, (void *) ret);
+
+		EXPECT_EQ((enum metacall_value_id) METACALL_NULL, (enum metacall_value_id) metacall_value_id(ret));
+
+		metacall_value_destroy(ret);
 
 		ret = metacall("cache_has_key","meta");