diff --git a/include/boost/config/compiler/gcc.hpp b/include/boost/config/compiler/gcc.hpp
index e1c33e0c..eeaf9982 100644
--- a/include/boost/config/compiler/gcc.hpp
+++ b/include/boost/config/compiler/gcc.hpp
@@ -115,7 +115,7 @@
 // Dynamic shared object (DSO) and dynamic-link library (DLL) support
 //
 #if __GNUC__ >= 4
-#  if defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
+#  if (defined(_WIN32) || defined(__WIN32__) || defined(WIN32)) && !defined(__CYGWIN__)
      // All Win32 development environments, including 64-bit Windows and MinGW, define 
      // _WIN32 or one of its variant spellings. Note that Cygwin is a POSIX environment,
      // so does not define _WIN32 or its variants.