diff --git a/lib/config-win32.h b/lib/config-win32.h
index 91c63bf23..bd66b56c9 100644
--- a/lib/config-win32.h
+++ b/lib/config-win32.h
@@ -279,6 +279,7 @@
 /* Define as the return type of signal handlers (int or void).  */
 #define RETSIGTYPE void
 
+#ifndef _SSIZE_T_DEFINED
 #if (defined(__WATCOMC__) && (__WATCOMC__ >= 1240)) || defined(__POCC__) || \
     defined(__MINGW32__)
 #elif defined(_WIN64)
@@ -286,6 +287,8 @@
 #else
 #define ssize_t int
 #endif
+#define _SSIZE_T_DEFINED
+#endif
 
 /* Define to 'int' if socklen_t is not an available 'typedefed' type */
 #ifndef HAVE_WS2TCPIP_H