- "R6RS custom binary port does not "
- "support `port-position'");
-
- offset += scm_to_int (result);
+ "R6RS custom binary port with "
+ "`port-position' support");
+ c_result = scm_to_int (result);
+ if (offset == 0)
+ /* We just want to know the current position. */
+ break;
+
+ offset += c_result;