diff --git a/eschalot.c b/eschalot.c
index ef918a8..d6c9f96 100644
--- a/eschalot.c
+++ b/eschalot.c
@@ -41,7 +41,7 @@
   #define le64toh(x) OSSwapLittleToHostInt64(x)
 #endif  /* __APPLE__ */
 
-#ifdef __linux__
+#if defined(__linux__) || defined(__CYGWIN__)
 # define _GNU_SOURCE
 # include <endian.h>
 #endif