diff --git a/_pytest/main.py b/_pytest/main.py
index 8654d7af627..76a4fc128e9 100644
--- a/_pytest/main.py
+++ b/_pytest/main.py
@@ -1,7 +1,5 @@
 """ core implementation of testing process: init, session, runtest loop. """
-import imp
 import os
-import re
 import sys
 
 import _pytest
@@ -25,8 +23,6 @@
 EXIT_USAGEERROR = 4
 EXIT_NOTESTSCOLLECTED = 5
 
-name_re = re.compile("^[a-zA-Z_]\w*$")
-
 def pytest_addoption(parser):
     parser.addini("norecursedirs", "directory patterns to avoid for recursion",
         type="args", default=['.*', 'CVS', '_darcs', '{arch}', '*.egg'])
@@ -649,36 +645,29 @@ def _recurse(self, path):
         return True
 
     def _tryconvertpyarg(self, x):
-        mod = None
-        path = [os.path.abspath('.')] + sys.path
-        for name in x.split('.'):
-            # ignore anything that's not a proper name here
-            # else something like --pyargs will mess up '.'
-            # since imp.find_module will actually sometimes work for it
-            # but it's supposed to be considered a filesystem path
-            # not a package
-            if name_re.match(name) is None:
-                return x
-            try:
-                fd, mod, type_ = imp.find_module(name, path)
-            except ImportError:
-                return x
-            else:
-                if fd is not None:
-                    fd.close()
+        """Convert a dotted module name to path.
 
-            if type_[2] != imp.PKG_DIRECTORY:
-                path = [os.path.dirname(mod)]
-            else:
-                path = [mod]
-        return mod
+        """
+        import pkgutil
+        try:
+            loader = pkgutil.find_loader(x)
+        except ImportError:
+            return x
+        if loader is None:
+            return x
+        try:
+            path = loader.get_filename()
+        except:
+            path = loader.modules[x][0].co_filename
+        if loader.is_package(x):
+            path = os.path.dirname(path)
+        return path
 
     def _parsearg(self, arg):
         """ return (fspath, names) tuple after checking the file exists. """
-        arg = str(arg)
-        if self.config.option.pyargs:
-            arg = self._tryconvertpyarg(arg)
         parts = str(arg).split("::")
+        if self.config.option.pyargs:
+            parts[0] = self._tryconvertpyarg(parts[0])
         relpath = parts[0].replace("/", os.sep)
         path = self.config.invocation_dir.join(relpath, abs=True)
         if not path.check():
diff --git a/testing/acceptance_test.py b/testing/acceptance_test.py
index 4e964503756..c66a1740f11 100644
--- a/testing/acceptance_test.py
+++ b/testing/acceptance_test.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import sys
 
 import _pytest._code
@@ -514,11 +515,20 @@ def test_pyargs_importerror(self, testdir, monkeypatch):
 
         result = testdir.runpytest("--pyargs", "tpkg.test_hello")
         assert result.ret != 0
-        # FIXME: It would be more natural to match NOT
-        # "ERROR*file*or*package*not*found*".
-        result.stdout.fnmatch_lines([
-            "*collected 0 items*"
-        ])
+
+        # Depending on whether the process running the test is the
+        # same as the process parsing the command-line arguments, the
+        # type of failure can be different:
+        if result.stderr.str() == '':
+            # Different processes
+            result.stdout.fnmatch_lines([
+                "collected*0*items*/*1*errors"
+            ])
+        else:
+            # Same process
+            result.stderr.fnmatch_lines([
+                "ERROR:*file*or*package*not*found:*tpkg.test_hello"
+            ])
 
     def test_cmdline_python_package(self, testdir, monkeypatch):
         monkeypatch.delenv('PYTHONDONTWRITEBYTECODE', False)
@@ -557,6 +567,68 @@ def join_pythonpath(what):
             "*not*found*test_hello*",
         ])
 
+    def test_cmdline_python_namespace_package(self, testdir, monkeypatch):
+        """
+        test --pyargs option with namespace packages (#1567)
+        """
+        monkeypatch.delenv('PYTHONDONTWRITEBYTECODE', raising=False)
+
+        search_path = []
+        for dirname in "hello", "world":
+            d = testdir.mkdir(dirname)
+            search_path.append(d)
+            ns = d.mkdir("ns_pkg")
+            ns.join("__init__.py").write(
+                "__import__('pkg_resources').declare_namespace(__name__)")
+            lib = ns.mkdir(dirname)
+            lib.ensure("__init__.py")
+            lib.join("test_{0}.py".format(dirname)). \
+                write("def test_{0}(): pass\n"
+                      "def test_other():pass".format(dirname))
+
+        # The structure of the test directory is now:
+        # .
+        # ├── hello
+        # │   └── ns_pkg
+        # │       ├── __init__.py
+        # │       └── hello
+        # │           ├── __init__.py
+        # │           └── test_hello.py
+        # └── world
+        #     └── ns_pkg
+        #         ├── __init__.py
+        #         └── world
+        #             ├── __init__.py
+        #             └── test_world.py
+
+        def join_pythonpath(*dirs):
+            cur = py.std.os.environ.get('PYTHONPATH')
+            if cur:
+                dirs += (cur,)
+            return ':'.join(str(p) for p in dirs)
+        monkeypatch.setenv('PYTHONPATH', join_pythonpath(*search_path))
+        for p in search_path:
+            monkeypatch.syspath_prepend(p)
+
+        # mixed module and filenames:
+        result = testdir.runpytest("--pyargs", "-v", "ns_pkg.hello", "world/ns_pkg")
+        assert result.ret == 0
+        result.stdout.fnmatch_lines([
+            "*test_hello.py::test_hello*PASSED",
+            "*test_hello.py::test_other*PASSED",
+            "*test_world.py::test_world*PASSED",
+            "*test_world.py::test_other*PASSED",
+            "*4 passed*"
+        ])
+
+        # specify tests within a module
+        result = testdir.runpytest("--pyargs", "-v", "ns_pkg.world.test_world::test_other")
+        assert result.ret == 0
+        result.stdout.fnmatch_lines([
+            "*test_world.py::test_other*PASSED",
+            "*1 passed*"
+        ])
+
     def test_cmdline_python_package_not_exists(self, testdir):
         result = testdir.runpytest("--pyargs", "tpkgwhatv")
         assert result.ret
@@ -697,4 +769,3 @@ def test_setup_function(self, testdir):
             * setup *test_1*
             * call *test_1*
         """)
-