diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 73ed4814..ccf5a337 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -363,6 +363,7 @@ endif (WITH_VISIBILITY_HIDDEN)
 
 if (MINGW)
     set_target_properties(ssh PROPERTIES LINK_FLAGS "-Wl,--enable-stdcall-fixup")
+    set_target_properties(ssh PROPERTIES COMPILE_FLAGS "-D_POSIX_SOURCE")
 endif ()