diff --git a/futility/futility.h b/futility/futility.h
index 18582c6..b31fd59 100644
--- a/futility/futility.h
+++ b/futility/futility.h
@@ -109,6 +109,7 @@
 			   uint32_t *maxlen);
 
 /* Updates HWID in GBB properly (and update digest if available). */
+struct vb2_gbb_header;
 int vb2_change_hwid(struct vb2_gbb_header *gbb, const char *hwid);
 
 /* For GBB v1.2 and later, update the hwid_digest */