diff --git a/libgphoto2_port/gphoto2/gphoto2-port-portability.h b/libgphoto2_port/gphoto2/gphoto2-port-portability.h
index b8b183573..eda812893 100644
--- a/libgphoto2_port/gphoto2/gphoto2-port-portability.h
+++ b/libgphoto2_port/gphoto2/gphoto2-port-portability.h
@@ -48,7 +48,9 @@
 
 #define __func__ __FUNCTION__
 
+#ifndef _SSIZE_T_DEFINED
 typedef SSIZE_T ssize_t;
+#endif
 
 /* Work-around for readdir() */
 typedef struct {