diff --git a/include/boost/test/execution_monitor.hpp b/include/boost/test/execution_monitor.hpp
index a757e37b..57fc7fcb 100644
--- a/include/boost/test/execution_monitor.hpp
+++ b/include/boost/test/execution_monitor.hpp
@@ -77,7 +77,7 @@
 
 #else // based on ISO C standard
 
-# if defined(__CYGWIN__) && defined(BOOST_CLANG)
+# if !defined(__CYGWIN__) && !defined(BOOST_CLANG)
 #   if defined(__SUNPRO_CC)
 #     include <stdio.h>
 #   endif