diff --git a/CHANGELOG b/CHANGELOG
index ecc93a3b9..3bff6ee6f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -104,9 +104,17 @@
 2.7.3 (compared to 2.7.2)
 -----------------------------
 
+- Allow 'dev', 'rc', or other non-integer version strings in `importorskip`.
+  Thanks to Eric Hunsberger for the PR.
+
 - fix issue856: consider --color parameter in all outputs (for example
   --fixtures). Thanks Barney Gale for the report and Bruno Oliveira for the PR.
 
+- fix issue855: passing str objects as `plugins` argument to pytest.main
+  is now interpreted as a module name to be imported and registered as a
+  plugin, instead of silently having no effect.
+  Thanks xmo-odoo for the report and Bruno Oliveira for the PR.
+
 - fix issue744: fix for ast.Call changes in Python 3.5+.  Thanks
   Guido van Rossum, Matthias Bussonnier, Stefan Zimmermann and
   Thomas Kluyver.
diff --git a/_pytest/config.py b/_pytest/config.py
index c8a79f6b5..492dbbc43 100644
--- a/_pytest/config.py
+++ b/_pytest/config.py
@@ -107,7 +107,10 @@ def _prepareconfig(args=None, plugins=None):
     try:
         if plugins:
             for plugin in plugins:
-                pluginmanager.register(plugin)
+                if isinstance(plugin, py.builtin._basestring):
+                    pluginmanager.consider_pluginarg(plugin)
+                else:
+                    pluginmanager.register(plugin)
         return pluginmanager.hook.pytest_cmdline_parse(
                 pluginmanager=pluginmanager, args=args)
     except BaseException:
diff --git a/_pytest/runner.py b/_pytest/runner.py
index 8accd3b0c..ad106b4b4 100644
--- a/_pytest/runner.py
+++ b/_pytest/runner.py
@@ -3,6 +3,8 @@ import bdb
 import sys
 from time import time
 
+from pkg_resources import parse_version
+
 import py
 import pytest
 from py._code.code import TerminalRepr
@@ -483,8 +485,6 @@ def importorskip(modname, minversion=None):
     """ return imported module if it has at least "minversion" as its
     __version__ attribute.  If no minversion is specified the a skip
     is only triggered if the module can not be imported.
-    Note that version comparison only works with simple version strings
-    like "1.2.3" but not "1.2.3.dev1" or others.
     """
     __tracebackhide__ = True
     compile(modname, '', 'eval') # to catch syntaxerrors
@@ -496,9 +496,7 @@ def importorskip(modname, minversion=None):
     if minversion is None:
         return mod
     verattr = getattr(mod, '__version__', None)
-    def intver(verstring):
-        return [int(x) for x in verstring.split(".")]
-    if verattr is None or intver(verattr) < intver(minversion):
+    if verattr is None or parse_version(verattr) < parse_version(minversion):
         skip("module %r has __version__ %r, required is: %r" %(
              modname, verattr, minversion))
     return mod
diff --git a/testing/acceptance_test.py b/testing/acceptance_test.py
index 346e57dd2..d845fd46a 100644
--- a/testing/acceptance_test.py
+++ b/testing/acceptance_test.py
@@ -1,3 +1,4 @@
+import sys
 import py, pytest
 
 class TestGeneralUsage:
@@ -371,6 +372,21 @@ class TestGeneralUsage:
             "*fixture 'invalid_fixture' not found",
         ])
 
+    def test_plugins_given_as_strings(self, tmpdir, monkeypatch):
+        """test that str values passed to main() as `plugins` arg
+        are interpreted as module names to be imported and registered.
+        #855.
+        """
+        with pytest.raises(ImportError) as excinfo:
+            pytest.main([str(tmpdir)], plugins=['invalid.module'])
+        assert 'invalid' in str(excinfo.value)
+
+        p = tmpdir.join('test_test_plugins_given_as_strings.py')
+        p.write('def test_foo(): pass')
+        mod = py.std.types.ModuleType("myplugin")
+        monkeypatch.setitem(sys.modules, 'myplugin', mod)
+        assert pytest.main(args=[str(tmpdir)], plugins=['myplugin']) == 0
+
 
 class TestInvocationVariants:
     def test_earlyinit(self, testdir):
diff --git a/testing/test_capture.py b/testing/test_capture.py
index 235bacae0..2b1fc69c8 100644
--- a/testing/test_capture.py
+++ b/testing/test_capture.py
@@ -649,7 +649,8 @@ def lsof_check():
     pid = os.getpid()
     try:
         out = py.process.cmdexec("lsof -p %d" % pid)
-    except py.process.cmdexec.Error:
+    except (py.process.cmdexec.Error, UnicodeDecodeError):
+        # about UnicodeDecodeError, see note on conftest.py 
         pytest.skip("could not run 'lsof'")
     yield
     out2 = py.process.cmdexec("lsof -p %d" % pid)
diff --git a/testing/test_runner.py b/testing/test_runner.py
index e62aea9f7..167ddc57b 100644
--- a/testing/test_runner.py
+++ b/testing/test_runner.py
@@ -439,7 +439,7 @@ def test_exception_printing_skip():
         s = excinfo.exconly(tryshort=True)
         assert s.startswith("Skipped")
 
-def test_importorskip():
+def test_importorskip(monkeypatch):
     importorskip = pytest.importorskip
     def f():
         importorskip("asdlkj")
@@ -457,7 +457,7 @@ def test_importorskip():
         pytest.raises(SyntaxError, "pytest.importorskip('x=y')")
         mod = py.std.types.ModuleType("hello123")
         mod.__version__ = "1.3"
-        sys.modules["hello123"] = mod
+        monkeypatch.setitem(sys.modules, "hello123", mod)
         pytest.raises(pytest.skip.Exception, """
             pytest.importorskip("hello123", minversion="1.3.1")
         """)
@@ -471,6 +471,19 @@ def test_importorskip_imports_last_module_part():
     ospath = pytest.importorskip("os.path")
     assert os.path == ospath
 
+def test_importorskip_dev_module(monkeypatch):
+    try:
+        mod = py.std.types.ModuleType("mockmodule")
+        mod.__version__ = '0.13.0.dev-43290'
+        monkeypatch.setitem(sys.modules, 'mockmodule', mod)
+        mod2 = pytest.importorskip('mockmodule', minversion='0.12.0')
+        assert mod2 == mod
+        pytest.raises(pytest.skip.Exception, """
+            pytest.importorskip('mockmodule1', minversion='0.14.0')""")
+    except pytest.skip.Exception:
+        print(py.code.ExceptionInfo())
+        pytest.fail("spurious skip")
+
 
 def test_pytest_cmdline_main(testdir):
     p = testdir.makepyfile("""