diff -Naurw backward.hpp backward.hpp
--- backward.hpp
+++ backward.hpp
@@ -344,7 +344,12 @@
 #include <thread>
 
 #include <basetsd.h>
+
+#ifdef _WIN64
 typedef SSIZE_T ssize_t;
+#else
+typedef int ssize_t;
+#endif
 
 #ifndef NOMINMAX
 #define NOMINMAX
 