diff --git a/shm.c b/shm.c
index b9cc325c..59dcb2ac 100644
--- a/shm.c
+++ b/shm.c
@@ -280,9 +280,16 @@ shm_fini(void)
     }
 }
 
+bool
+shm_can_scroll(void)
+{
+    return can_punch_hole;
+}
+
 bool
 shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows)
 {
+    assert(can_punch_hole);
     assert(buf->busy);
     assert(buf->pix);
     assert(buf->wl_buf);
diff --git a/shm.h b/shm.h
index 2b3a9b19..6801ed93 100644
--- a/shm.h
+++ b/shm.h
@@ -32,6 +32,7 @@ struct buffer *shm_get_buffer(
     struct wl_shm *shm, int width, int height, unsigned long cookie);
 void shm_fini(void);
 
+bool shm_can_scroll(void);
 bool shm_scroll(struct wl_shm *shm, struct buffer *buf, int rows);
 
 void shm_purge(struct wl_shm *shm, unsigned long cookie);