diff --git a/Tools/ardupilotwaf/boards.py b/Tools/ardupilotwaf/boards.py
index 82982c9ab65ec..045a3513eea9a 100644
--- a/Tools/ardupilotwaf/boards.py
+++ b/Tools/ardupilotwaf/boards.py
@@ -1021,8 +1021,7 @@ def expand_path(p):
                          '-fno-inline-functions',
                          '-mlongcalls',
                          '-fsingle-precision-constant', # force const vals to be float , not double. so 100.0 means 100.0f 
-                         '-fno-threadsafe-statics',
-                         '-DCYGWIN_BUILD']
+                         '-fno-threadsafe-statics']
         env.CXXFLAGS.remove('-Werror=undef')
         env.CXXFLAGS.remove('-Werror=shadow')