diff --git a/_pytest/assertion/rewrite.py b/_pytest/assertion/rewrite.py
index f7e255efd..79943cc53 100644
--- a/_pytest/assertion/rewrite.py
+++ b/_pytest/assertion/rewrite.py
@@ -11,7 +11,6 @@ import re
 import struct
 import sys
 import types
-from fnmatch import fnmatch
 
 import py
 from _pytest.assertion import util
@@ -167,7 +166,7 @@ class AssertionRewritingHook(object):
             # latter might trigger an import to fnmatch.fnmatch
             # internally, which would cause this method to be
             # called recursively
-            if fnmatch(fn_pypath.basename, pat):
+            if fn_pypath.fnmatch(pat):
                 state.trace("matched test file %r" % (fn,))
                 return True
 
diff --git a/changelog/2121.bugfix b/changelog/2121.bugfix
new file mode 100644
index 000000000..15fd7706c
--- /dev/null
+++ b/changelog/2121.bugfix
@@ -0,0 +1 @@
+Respect ``python_files`` in assertion rewriting.
diff --git a/setup.py b/setup.py
index a71692c25..751868c04 100644
--- a/setup.py
+++ b/setup.py
@@ -43,7 +43,7 @@ def has_environment_marker_support():
 
 
 def main():
-    install_requires = ['py>=1.4.29', 'setuptools']  # pluggy is vendored in _pytest.vendored_packages
+    install_requires = ['py>=1.4.33', 'setuptools']  # pluggy is vendored in _pytest.vendored_packages
     extras_require = {}
     if has_environment_marker_support():
         extras_require[':python_version=="2.6"'] = ['argparse']
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index 11b5ce051..8aee520b3 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -956,3 +956,17 @@ class TestIssue925(object):
         result = testdir.runpytest()
         result.stdout.fnmatch_lines('*E*assert True == ((False == True) == True)')
 
+
+class TestIssue2121():
+    def test_simple(self, testdir):
+        testdir.tmpdir.join("tests/file.py").ensure().write("""
+def test_simple_failure():
+    assert 1 + 1 == 3
+""")
+        testdir.tmpdir.join("pytest.ini").write(py.std.textwrap.dedent("""
+            [pytest]
+            python_files = tests/**.py
+        """))
+
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines('*E*assert (1 + 1) == 3')