diff --git a/src/libdiskfs/ffs.c b/src/libdiskfs/ffs.c
index 099c7bb..ceb6052 100644
--- a/src/libdiskfs/ffs.c
+++ b/src/libdiskfs/ffs.c
@@ -107,6 +107,7 @@
 		if((fs->ufs = checkfsblk(fsblk)) > 0)
 			goto okay;
 		blockput(b);
+		b = nil;
 	}
 	goto error;