diff --git a/src/allmydata/storage/immutable.py b/src/allmydata/storage/immutable.py
index 8a7a5a966..7cfb7a1bf 100644
--- a/src/allmydata/storage/immutable.py
+++ b/src/allmydata/storage/immutable.py
@@ -233,7 +233,7 @@ class ShareFile(object):
 @implementer(RIBucketWriter)
 class BucketWriter(Referenceable):  # type: ignore # warner/foolscap#78
 
-    def __init__(self, ss, incominghome, finalhome, max_size, lease_info):
+    def __init__(self, ss, incominghome, finalhome, max_size, lease_info, clock):
         self.ss = ss
         self.incominghome = incominghome
         self.finalhome = finalhome
@@ -245,12 +245,13 @@ class BucketWriter(Referenceable):  # type: ignore # warner/foolscap#78
         # added by simultaneous uploaders
         self._sharefile.add_lease(lease_info)
         self._already_written = RangeMap()
+        self._clock = clock
 
     def allocated_size(self):
         return self._max_size
 
     def remote_write(self, offset, data):
-        start = time.time()
+        start = self._clock.seconds()
         precondition(not self.closed)
         if self.throw_out_all_data:
             return
@@ -268,12 +269,12 @@ class BucketWriter(Referenceable):  # type: ignore # warner/foolscap#78
         self._sharefile.write_share_data(offset, data)
 
         self._already_written.set(True, offset, end)
-        self.ss.add_latency("write", time.time() - start)
+        self.ss.add_latency("write", self._clock.seconds() - start)
         self.ss.count("write")
 
     def remote_close(self):
         precondition(not self.closed)
-        start = time.time()
+        start = self._clock.seconds()
 
         fileutil.make_dirs(os.path.dirname(self.finalhome))
         fileutil.rename(self.incominghome, self.finalhome)
@@ -306,7 +307,7 @@ class BucketWriter(Referenceable):  # type: ignore # warner/foolscap#78
 
         filelen = os.stat(self.finalhome)[stat.ST_SIZE]
         self.ss.bucket_writer_closed(self, filelen)
-        self.ss.add_latency("close", time.time() - start)
+        self.ss.add_latency("close", self._clock.seconds() - start)
         self.ss.count("close")
 
     def disconnected(self):
diff --git a/src/allmydata/storage/server.py b/src/allmydata/storage/server.py
index 499d47276..080c1aea1 100644
--- a/src/allmydata/storage/server.py
+++ b/src/allmydata/storage/server.py
@@ -347,7 +347,8 @@ class StorageServer(service.MultiService, Referenceable):
             elif (not limited) or (remaining_space >= max_space_per_bucket):
                 # ok! we need to create the new share file.
                 bw = BucketWriter(self, incominghome, finalhome,
-                                  max_space_per_bucket, lease_info)
+                                  max_space_per_bucket, lease_info,
+                                  clock=self._clock)
                 if self.no_storage:
                     bw.throw_out_all_data = True
                 bucketwriters[shnum] = bw
diff --git a/src/allmydata/test/test_storage.py b/src/allmydata/test/test_storage.py
index e143bec63..36c776fba 100644
--- a/src/allmydata/test/test_storage.py
+++ b/src/allmydata/test/test_storage.py
@@ -128,7 +128,7 @@ class Bucket(unittest.TestCase):
 
     def test_create(self):
         incoming, final = self.make_workdir("test_create")
-        bw = BucketWriter(self, incoming, final, 200, self.make_lease())
+        bw = BucketWriter(self, incoming, final, 200, self.make_lease(), Clock())
         bw.remote_write(0, b"a"*25)
         bw.remote_write(25, b"b"*25)
         bw.remote_write(50, b"c"*25)
@@ -137,7 +137,7 @@ class Bucket(unittest.TestCase):
 
     def test_readwrite(self):
         incoming, final = self.make_workdir("test_readwrite")
-        bw = BucketWriter(self, incoming, final, 200, self.make_lease())
+        bw = BucketWriter(self, incoming, final, 200, self.make_lease(), Clock())
         bw.remote_write(0, b"a"*25)
         bw.remote_write(25, b"b"*25)
         bw.remote_write(50, b"c"*7) # last block may be short
@@ -155,7 +155,7 @@ class Bucket(unittest.TestCase):
             incoming, final = self.make_workdir(
                 "test_write_past_size_errors-{}".format(i)
             )
-            bw = BucketWriter(self, incoming, final, 200, self.make_lease())
+            bw = BucketWriter(self, incoming, final, 200, self.make_lease(), Clock())
             with self.assertRaises(DataTooLargeError):
                 bw.remote_write(offset, b"a" * length)
 
@@ -174,7 +174,7 @@ class Bucket(unittest.TestCase):
         expected_data = b"".join(bchr(i) for i in range(100))
         incoming, final = self.make_workdir("overlapping_writes_{}".format(uuid4()))
         bw = BucketWriter(
-            self, incoming, final, length, self.make_lease(),
+            self, incoming, final, length, self.make_lease(), Clock()
         )
         # Three writes: 10-19, 30-39, 50-59. This allows for a bunch of holes.
         bw.remote_write(10, expected_data[10:20])
@@ -212,7 +212,7 @@ class Bucket(unittest.TestCase):
         length = 100
         incoming, final = self.make_workdir("overlapping_writes_{}".format(uuid4()))
         bw = BucketWriter(
-            self, incoming, final, length, self.make_lease(),
+            self, incoming, final, length, self.make_lease(), Clock()
         )
         # Three writes: 10-19, 30-39, 50-59. This allows for a bunch of holes.
         bw.remote_write(10, b"1" * 10)
@@ -312,7 +312,7 @@ class BucketProxy(unittest.TestCase):
         final = os.path.join(basedir, "bucket")
         fileutil.make_dirs(basedir)
         fileutil.make_dirs(os.path.join(basedir, "tmp"))
-        bw = BucketWriter(self, incoming, final, size, self.make_lease())
+        bw = BucketWriter(self, incoming, final, size, self.make_lease(), Clock())
         rb = RemoteBucket(bw)
         return bw, rb, final