diff --git a/britney.py b/britney.py
index af8af0f..9d42876 100755
--- a/britney.py
+++ b/britney.py
@@ -188,6 +188,7 @@ import os
 import sys
 import time
 import optparse
+import copy
 
 import apt_pkg
 
@@ -1040,9 +1041,11 @@ class Britney(object):
         """Merge sources from `source' into partial suite `target'."""
         source_sources = self.sources[source]
         target_sources = self.sources[target]
+        # we need complete copies here, as we might later find some binaries
+        # which are only in unstable
         for pkg, value in source_sources.items():
             if pkg not in target_sources:
-                target_sources[pkg] = value
+                target_sources[pkg] = copy.deepcopy(value)
 
     def merge_binaries(self, source, target, arch):
         """Merge `arch' binaries from `source' into partial suite `target'."""
diff --git a/tests/test_autopkgtest.py b/tests/test_autopkgtest.py
index e563689..00af277 100755
--- a/tests/test_autopkgtest.py
+++ b/tests/test_autopkgtest.py
@@ -873,6 +873,21 @@ class T(TestBase):
         self.assertEqual(self.pending_requests, {})
         self.assertEqual(self.amqp_requests, set())
 
+    def test_same_version_binary_in_unstable(self):
+        '''binary from new architecture in unstable with testing version'''
+
+        # i386 is in testing already, but amd64 just recently built and is in unstable
+        self.data.add_src('brown', False, {'Testsuite': 'autopkgtest'})
+        self.data.add('brown', False, {'Architecture': 'i386'}, add_src=False)
+        self.data.add('brown', True, {'Architecture': 'amd64'}, add_src=False)
+
+        exc = self.do_test(
+            # we need some other package to create unstable Sources
+            [('lightgreen', {'Version': '2'}, 'autopkgtest')],
+            {'brown': (True, {})}
+            )[1]
+        self.assertEqual(exc['brown']['item-name'], 'brown/amd64')
+
     def test_package_pair_running(self):
         '''Two packages in unstable that need to go in together (running)'''