diff --git a/libcxx/src/thread.cpp b/libcxx/src/thread.cpp
index 6aad558abaad..bd27f2878383 100644
--- a/libcxx/src/thread.cpp
+++ b/libcxx/src/thread.cpp
@@ -17,9 +17,9 @@
 #include "limits"
 #include <sys/types.h>
 #if !defined(_WIN32)
-# if !defined(__sun__) && !defined(__linux__) && !defined(_AIX) && !defined(__native_client__)
+# if !defined(__sun__) && !defined(__linux__) && !defined(_AIX) && !defined(__native_client__) && !defined(__CloudABI__)
 #   include <sys/sysctl.h>
-# endif // !defined(__sun__) && !defined(__linux__) && !defined(_AIX) && !defined(__native_client__)
+# endif // !defined(__sun__) && !defined(__linux__) && !defined(_AIX) && !defined(__native_client__) && !defined(__CloudABI__)
 # include <unistd.h>
 #endif // !_WIN32