Index: src/thread.cpp
===================================================================
--- src/thread.cpp
+++ src/thread.cpp
@@ -16,10 +16,17 @@
 #include "future"
 #include "limits"
 #include <sys/types.h>
+
+#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
+# if !defined(__CloudABI__)
+#   include <sys/param.h>
+#   if defined(BSD)
+#     include <sys/sysctl.h>
+#   endif // defined(BSD)
+# endif // !defined(__CloudABI__)
+#endif // defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
+
 #if !defined(_WIN32)
-# 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__) && !defined(__CloudABI__)
 # include <unistd.h>
 #endif // !_WIN32