diff --git a/src/buffer.c b/src/buffer.c
index 14eac92..93f9245 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5777,7 +5777,7 @@
 bt_quickfix(buf_T *buf UNUSED)
 {
 #ifdef FEAT_QUICKFIX
-    return buf != NULL && buf->b_p_bt[0] == 'q';
+    return buf != NULL && buf_valid(buf) && buf->b_p_bt[0] == 'q';
 #else
     return FALSE;
 #endif