diff --git a/src/buffer.c b/src/buffer.c
index 2f574e0..e8e1a6d 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -372,7 +372,7 @@
 set_bufref(bufref_T *bufref, buf_T *buf)
 {
     bufref->br_buf = buf;
-    bufref->br_fnum = buf->b_fnum;
+    bufref->br_fnum = buf == NULL ? 0 : buf->b_fnum;
     bufref->br_buf_free_count = buf_free_count;
 }