improve mcheck availability check
diff --git a/c_gen/templates/locitest/test_setup_from_add.c b/c_gen/templates/locitest/test_setup_from_add.c
index d8911f3..0b07076 100644
--- a/c_gen/templates/locitest/test_setup_from_add.c
+++ b/c_gen/templates/locitest/test_setup_from_add.c
@@ -33,10 +33,11 @@
#include <locitest/test_common.h>
-#if !defined(__APPLE__)
+/* mcheck is a glibc extension */
+#if defined(__linux__)
#include <mcheck.h>
#define MCHECK_INIT mcheck(NULL)
-#else /* mcheck not available under OS X */
+#else
#define MCHECK_INIT do { } while (0)
#endif