diff --git a/unistd.h b/unistd.h
new file mode 100644
index 0000000..f0ce70d
--- /dev/null
+++ b/unistd.h
@@ -0,0 +1,8 @@
+/* See http://llvm.org/bugs/show_bug.cgi?id=4746 */
+#ifdef __block
+#	undef __block
+#	include_next "unistd.h"
+#	define __block __attribute__((__blocks__(byref)))
+#else
+#	include_next "unistd.h"
+#endif