diff --git a/include/config-win.h b/include/config-win.h
index 364c4f92134..431bfcfa702 100644
--- a/include/config-win.h
+++ b/include/config-win.h
@@ -145,12 +145,23 @@ typedef __int64 os_off_t;
 #ifdef _WIN64
 typedef UINT_PTR rf_SetTimer;
 #else
-#ifndef HAVE_SIZE_T
-typedef unsigned int size_t;
-#endif
 typedef uint rf_SetTimer;
 #endif
 
+#ifndef HAVE_SIZE_T
+#ifndef _SIZE_T_DEFINED
+typedef SIZE_T size_t;
+#define _SIZE_T_DEFINED
+#endif
+#endif
+
+#ifndef HAVE_SSIZE_T
+#ifndef _SSIZE_T_DEFINED
+typedef SSIZE_T ssize_t;
+#define _SSIZE_T_DEFINED
+#endif
+#endif
+
 #define Socket_defined
 #define my_socket SOCKET
 #define SIGPIPE SIGINT