diff --git a/include/uv.h b/include/uv.h
index 0ede3083..f8e1d273 100644
--- a/include/uv.h
+++ b/include/uv.h
@@ -122,7 +122,8 @@ typedef intptr_t ssize_t;
   XX( 51, ELOOP, "too many symbolic links encountered") \
   XX( 52, EXDEV, "cross-device link not permitted") \
   XX( 53, ENOTEMPTY, "directory not empty") \
-  XX( 54, ENOSPC, "no space left on device")
+  XX( 54, ENOSPC, "no space left on device") \
+  XX( 55, EIO, "i/o error")
 
 
 #define UV_ERRNO_GEN(val, name, s) UV_##name = val,