improve mcheck availability check
diff --git a/c_gen/templates/locitest/main.c b/c_gen/templates/locitest/main.c
index df80f9f..3b24035 100644
--- a/c_gen/templates/locitest/main.c
+++ b/c_gen/templates/locitest/main.c
@@ -9,10 +9,11 @@
#include <locitest/unittest.h>
#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