diff --git a/src/system/libroot/posix/musl/arch/m68k/atomic_arch.h b/src/system/libroot/posix/musl/arch/m68k/atomic_arch.h
new file mode 100644
index 0000000000..b369649a1a
--- /dev/null
+++ b/src/system/libroot/posix/musl/arch/m68k/atomic_arch.h
@@ -0,0 +1,8 @@
+#define a_cas a_cas
+static inline int a_cas(volatile int *p, int t, int s)
+{
+	__asm__ __volatile__ (
+		"cas.l %0, %2, (%1)"
+		: "+d"(t) : "a"(p), "d"(s) : "memory", "cc");
+	return t;
+}