diff --git a/include/c99_alloca.h b/include/c99_alloca.h
index ed66fda0132..5a3b8c19abb 100644
--- a/include/c99_alloca.h
+++ b/include/c99_alloca.h
@@ -35,7 +35,7 @@
 
 #  define alloca _alloca
 
-#elif defined(__sun)
+#elif defined(__sun) || defined(__CYGWIN__)
 
 #  include <alloca.h>