diff --git a/src/allmydata/encode.py b/src/allmydata/encode.py
index 246bf8b40..ce470c953 100644
--- a/src/allmydata/encode.py
+++ b/src/allmydata/encode.py
@@ -73,7 +73,7 @@ class Encoder(object):
     NEEDED_SHARES = 25
     SHARES_OF_HAPPINESS = 75
     TOTAL_SHARES = 100
-    MAX_SEGMENT_SIZE = 2*MiB
+    MAX_SEGMENT_SIZE = 1*MiB
 
     def __init__(self, options={}):
         object.__init__(self)
diff --git a/src/allmydata/interfaces.py b/src/allmydata/interfaces.py
index 5462d0015..2b4f4829f 100644
--- a/src/allmydata/interfaces.py
+++ b/src/allmydata/interfaces.py
@@ -14,7 +14,7 @@ FURL = StringConstraint(1000)
 StorageIndex = StringConstraint(32)
 URI = StringConstraint(300) # kind of arbitrary
 MAX_BUCKETS = 200  # per peer
-ShareData = StringConstraint(700000) # 2MB segment / k=3 = 670kB
+ShareData = StringConstraint(400000) # 1MB segment / k=3 = 334kB
 URIExtensionData = StringConstraint(1000)
 
 class RIIntroducerClient(RemoteInterface):