diff --git a/src/magic.h.in b/src/magic.h.in
index 230fcbd..37d5542 100644
--- a/src/magic.h.in
+++ b/src/magic.h.in
@@ -28,6 +28,11 @@
 
 #include <sys/types.h>
 
+#ifdef _MSC_VER
+#include <BaseTsd.h>
+typedef SSIZE_T ssize_t;
+#endif
+
 #define	MAGIC_NONE		0x0000000 /* No flags */
 #define	MAGIC_DEBUG		0x0000001 /* Turn on debugging */
 #define	MAGIC_SYMLINK		0x0000002 /* Follow symlinks */