diff --git a/ringbuf.h b/ringbuf.h
index c72bfae..c56bd19 100644
--- a/ringbuf.h
+++ b/ringbuf.h
@@ -28,6 +28,9 @@
 
 #include <stddef.h>
 #include <sys/types.h>
+#ifdef _MSC_VER
+	typedef ptrdiff_t ssize_t;
+#endif
 
 typedef struct ringbuf_t *ringbuf_t;