--- /dev/null
+++ libmalloc/libmalloc-409.40.6/tests/checkfix.c
@@ -0,0 +1,27 @@
+#include <stdlib.h>
+#include <darwintest.h>
+#include <malloc_private.h>
+
+T_DECL(malloc_checkfix_zero_on_free, "Test malloc_zero_on_free_disable() SPI",
+		T_META_ENVVAR("MallocZeroOnFree=1"))
+{
+	// Drive some activity up front
+	void *p1 = malloc(16);
+	T_ASSERT_NOTNULL(p1, "malloc 1");
+	void *p2 = malloc(512);
+	T_ASSERT_NOTNULL(p1, "malloc 2");
+
+	free(p2);
+
+	// Call the checkfix SPI
+	malloc_zero_on_free_disable();
+
+	// Drive some more activity
+	void *p3 = calloc(1, 512);
+	T_ASSERT_NOTNULL(p3, "calloc 1");
+
+	free(p3);
+	free(p1);
+
+	T_PASS("Reached the end");
+}