diff --git a/googletest/CMakeLists.txt b/googletest/CMakeLists.txt
index 60556d66..a94e0815 100644
--- a/googletest/CMakeLists.txt
+++ b/googletest/CMakeLists.txt
@@ -205,6 +205,10 @@ if (gtest_build_tests)
   cxx_test(googletest-param-test-test gtest
     test/googletest-param-test2-test.cc)
   cxx_test(googletest-port-test gtest_main)
+  if (CYGWIN)
+    cxx_test(gtest_cygwin_strict_test gtest_main)
+    set_property(TARGET gtest_cygwin_strict_test PROPERTY CXX_EXTENSIONS OFF)
+  endif()
   cxx_test(gtest_pred_impl_unittest gtest_main)
   cxx_test(gtest_premature_exit_test gtest
     test/gtest_premature_exit_test.cc)
diff --git a/googletest/include/gtest/internal/gtest-port.h b/googletest/include/gtest/internal/gtest-port.h
index 154be3c1..56768a33 100644
--- a/googletest/include/gtest/internal/gtest-port.h
+++ b/googletest/include/gtest/internal/gtest-port.h
@@ -272,6 +272,10 @@
 // GCC15 warns that <ciso646> is deprecated in C++17 and suggests using
 // <version> instead, even though <version> is not available in C++17 mode prior
 // to GCC9.
+#if defined(__CYGWIN__) && defined(__STRICT_ANSI__) && !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200809L
+#endif
+
 #if GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L || \
     GTEST_INTERNAL_HAS_INCLUDE(<version>)
 #include <version>  // C++20 or <version> support.
diff --git a/googletest/test/gtest_cygwin_strict_test.cc b/googletest/test/gtest_cygwin_strict_test.cc
new file mode 100644
index 00000000..84dff515
--- /dev/null
+++ b/googletest/test/gtest_cygwin_strict_test.cc
@@ -0,0 +1,3 @@
+#include "gtest/gtest.h"
+
+TEST(CygwinStrictStandardTest, PortHeaderCompiles) { SUCCEED(); }