Index: sys/rump/librump/rumpvfs/rumpfs.c
===================================================================
RCS file: /cvsroot/src/sys/rump/librump/rumpvfs/rumpfs.c,v
retrieving revision 1.146
diff -p -u -r1.146 rumpfs.c
--- sys/rump/librump/rumpvfs/rumpfs.c	11 Apr 2017 14:25:01 -0000	1.146
+++ sys/rump/librump/rumpvfs/rumpfs.c	16 Apr 2017 04:59:40 -0000
@@ -945,6 +945,22 @@ rump_vop_setattr(void *v)
 		rn->rn_data = newdata;
 		rn->rn_dlen = newlen;
 		uvm_vnp_setsize(vp, newlen);
+
+		/*
+		 * If the caller left either ctime or atime
+		 * unspecified, update them since we just modified the
+		 * file.
+		 */
+		if (vap->va_ctime.tv_sec == (time_t)VNOVAL ||
+		    vap->va_mtime.tv_sec == (time_t)VNOVAL) {
+			struct timespec now;
+
+			vfs_timestamp(&now);
+			if (vap->va_ctime.tv_sec == (time_t)VNOVAL)
+				rn->rn_va.va_ctime = now;
+			if (vap->va_mtime.tv_sec == (time_t)VNOVAL)
+				rn->rn_va.va_mtime = now;
+		}
 	}
 	return 0;
 }