diff --git a/src/network/bmobject.py b/src/network/bmobject.py
index 12b997d7..c6684f3c 100644
--- a/src/network/bmobject.py
+++ b/src/network/bmobject.py
@@ -36,6 +36,12 @@ class BMObjectUnwantedStreamError(Exception):
     errorCodes = ("Object in unwanted stream")
 
 
+class BMObjectInvalidStreamError(Exception):
+    """Exception indicating the object is in a stream
+    outside of specification."""
+    errorCodes = ("Object in invalid stream")
+
+
 class BMObjectInvalidError(Exception):
     """The object's data does not match object specification."""
     errorCodes = ("Invalid object")
@@ -106,6 +112,9 @@ class BMObject(object):  # pylint: disable=too-many-instance-attributes
                 'The streamNumber %i isn\'t one we are interested in.',
                 self.streamNumber)
             raise BMObjectUnwantedStreamError()
+        if self.streamNumber < protocol.MIN_VALID_STREAM \
+           or self.streamNumber > protocol.MAX_VALID_STREAM:
+            raise BMObjectInvalidStreamError()
 
     def checkAlreadyHave(self):
         """
diff --git a/src/network/bmproto.py b/src/network/bmproto.py
index 009c471f..ee43523d 100644
--- a/src/network/bmproto.py
+++ b/src/network/bmproto.py
@@ -22,7 +22,8 @@ from network.advanceddispatcher import AdvancedDispatcher
 from network.bmobject import (
     BMObject, BMObjectAlreadyHaveError, BMObjectExpiredError,
     BMObjectInsufficientPOWError, BMObjectInvalidDataError,
-    BMObjectInvalidError, BMObjectUnwantedStreamError
+    BMObjectInvalidError, BMObjectUnwantedStreamError,
+    BMObjectInvalidStreamError
 )
 from network.constants import (
     ADDRESS_ALIVE, MAX_MESSAGE_SIZE, MAX_OBJECT_COUNT,
@@ -409,6 +410,10 @@ class BMProto(AdvancedDispatcher, ObjectTracker):
                 self.object.inventoryHash, acceptmismatch)
             if not acceptmismatch:
                 raise
+        except BMObjectInvalidStreamError:
+            BMProto.stopDownloadingObject(
+                self.object.inventoryHash)
+            raise
 
         try:
             self.object.checkObjectByType()
diff --git a/src/protocol.py b/src/protocol.py
index 291d4ebd..4cab2dd6 100644
--- a/src/protocol.py
+++ b/src/protocol.py
@@ -90,6 +90,11 @@ def isBitSetWithinBitfield(fourByteString, n):
     x, = unpack('>L', fourByteString)
     return x & 2**n != 0
 
+# Streams
+
+
+MIN_VALID_STREAM = 1
+MAX_VALID_STREAM = 2**63 - 1
 
 # IP addresses