1 files changed, 2 insertions, 0 deletions
diff --git a/io.c b/io.c
index 7663733d1e..8b0e51b460 100644
--- a/io.c
+++ b/io.c
@@ -1283,6 +1283,8 @@ io_getpartial(int argc, VALUE *argv, VALUE io, int nonblock)
                 goto again;
             rb_sys_fail(fptr->path);
         }
+        if (fptr->f) /* update pos in FILE structure [ruby-core:21561] */
+            fflush(fptr->f);
     }
     rb_str_resize(str, n);