diff --git a/mongoose.c b/mongoose.c
index 0cacdfed..d733d41a 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -48,7 +48,9 @@
 #define _INTEGRAL_MAX_BITS 64   // Enable _stati64() on Windows
 #define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005+
 #undef WIN32_LEAN_AND_MEAN      // Let windows.h always include winsock2.h
+#ifdef __Linux__
 #define _XOPEN_SOURCE 600       // For flockfile() on Linux
+#endif
 #define __STDC_FORMAT_MACROS    // <inttypes.h> wants this for C++
 #define __STDC_LIMIT_MACROS     // C++ wants that for INT64_MAX
 #ifndef _LARGEFILE_SOURCE