diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 0841ddcd61..797ae1ff5d 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -1560,10 +1560,9 @@ def do_activate(self, force=False):
 
         # Activate any package dependencies that are also extensions.
         if not force:
-            for spec in self.spec.traverse(root=False, deptype='run'):
-                if spec.package.extends(self.extendee_spec):
-                    if not spec.package.activated:
-                        spec.package.do_activate(force=force)
+            for spec in self.dependency_activations():
+                if not spec.package.activated:
+                    spec.package.do_activate(force=force)
 
         self.extendee_spec.package.activate(self, **self.extendee_args)
 
@@ -1571,6 +1570,10 @@ def do_activate(self, force=False):
         tty.msg("Activated extension %s for %s" %
                 (self.spec.short_spec, self.extendee_spec.format("$_$@$+$%@")))
 
+    def dependency_activations(self):
+        return (spec for spec in self.spec.traverse(root=False, deptype='run')
+                if spec.package.extends(self.extendee_spec))
+
     def activate(self, extension, **kwargs):
         """Symlinks all files from the extension into extendee's install dir.
 
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 8f315fdabf..059653a72a 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -2011,8 +2011,8 @@ def satisfies(self, other, deps=True, strict=False, strict_deps=False):
         other = self._autospec(other)
 
         # The only way to satisfy a concrete spec is to match its hash exactly.
-        if other._concrete:
-            return self._concrete and self.dag_hash() == other.dag_hash()
+        if other.concrete:
+            return self.concrete and self.dag_hash() == other.dag_hash()
 
         # A concrete provider can satisfy a virtual dependency.
         if not self.virtual and other.virtual:
diff --git a/lib/spack/spack/test/packages.py b/lib/spack/spack/test/packages.py
index 6ae8a33a24..bc1f438e44 100644
--- a/lib/spack/spack/test/packages.py
+++ b/lib/spack/spack/test/packages.py
@@ -108,6 +108,13 @@ def test_inheritance_of_diretives():
     assert 'mpi' in s
 
 
+def test_dependency_extensions():
+    s = Spec('extension2')
+    s.concretize()
+    deps = set(x.name for x in s.package.dependency_activations())
+    assert deps == set(['extension1'])
+
+
 def test_import_class_from_package(builtin_mock):
     from spack.pkg.builtin.mock.mpich import Mpich  # noqa
 
diff --git a/lib/spack/spack/test/spec_semantics.py b/lib/spack/spack/test/spec_semantics.py
index 84c8650f15..2f3b2b1b8d 100644
--- a/lib/spack/spack/test/spec_semantics.py
+++ b/lib/spack/spack/test/spec_semantics.py
@@ -287,6 +287,14 @@ def test_unsatisfiable_compiler_flag(self):
         # 'mpich' is concrete:
         check_unsatisfiable('mpich', 'mpich cppflags="-O3"', True)
 
+    def test_copy_satisfies_transitive(self):
+        spec = Spec('dttop')
+        spec.concretize()
+        copy = spec.copy()
+        for s in spec.traverse():
+            assert s.satisfies(copy[s.name])
+            assert copy[s.name].satisfies(s) 
+
     def test_unsatisfiable_compiler_flag_mismatch(self):
         # No matchi in specs
         check_unsatisfiable(
diff --git a/var/spack/repos/builtin.mock/packages/extendee/package.py b/var/spack/repos/builtin.mock/packages/extendee/package.py
new file mode 100644
index 0000000000..f86bcf7de5
--- /dev/null
+++ b/var/spack/repos/builtin.mock/packages/extendee/package.py
@@ -0,0 +1,39 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extendee(Package):
+    """A package with extensions"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extendee-1.0.tar.gz"
+
+    extendable = True
+
+    version('1.0', 'hash-extendee-1.0')
+
+    def install(self, spec, prefix):
+        pass
diff --git a/var/spack/repos/builtin.mock/packages/extension1/package.py b/var/spack/repos/builtin.mock/packages/extension1/package.py
new file mode 100644
index 0000000000..d3babc6ce4
--- /dev/null
+++ b/var/spack/repos/builtin.mock/packages/extension1/package.py
@@ -0,0 +1,39 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extension1(Package):
+    """A package which extends another package"""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extension1-1.0.tar.gz"
+
+    extends('extendee')
+
+    version('1.0', 'hash-extension1-1.0')
+
+    def install(self, spec, prefix):
+        pass
diff --git a/var/spack/repos/builtin.mock/packages/extension2/package.py b/var/spack/repos/builtin.mock/packages/extension2/package.py
new file mode 100644
index 0000000000..fcb23ab8ed
--- /dev/null
+++ b/var/spack/repos/builtin.mock/packages/extension2/package.py
@@ -0,0 +1,41 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Extension2(Package):
+    """A package which extends another package. It also depends on another
+       package which extends the same package."""
+
+    homepage = "http://www.example.com"
+    url      = "http://www.example.com/extension2-1.0.tar.gz"
+
+    extends('extendee')
+    depends_on('extension1', type=('build', 'run'))
+
+    version('1.0', 'hash-extension2-1.0')
+
+    def install(self, spec, prefix):
+        pass