Use IOError.
diff --git a/Objects/object.c b/Objects/object.c
index 2000f03..78541d1 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -86,7 +86,7 @@
 	}
 	if (ret == 0) {
 		if (ferror(fp)) {
-			err_errno(RuntimeError);
+			err_errno(IOError);
 			clearerr(fp);
 			ret = -1;
 		}