diff --git a/_pytest/main.py b/_pytest/main.py
index 452079762..002dc59a7 100644
--- a/_pytest/main.py
+++ b/_pytest/main.py
@@ -251,6 +251,24 @@ class Node(object):
     def teardown(self):
         pass
 
+    def _memoizedcall(self, attrname, function):
+        exattrname = "_ex_" + attrname
+        failure = getattr(self, exattrname, None)
+        if failure is not None:
+            py.builtin._reraise(failure[0], failure[1], failure[2])
+        if hasattr(self, attrname):
+            return getattr(self, attrname)
+        try:
+            res = function()
+        except py.builtin._sysex:
+            raise
+        except:
+            failure = py.std.sys.exc_info()
+            setattr(self, exattrname, failure)
+            raise
+        setattr(self, attrname, res)
+        return res
+
     def listchain(self):
         """ return list of all parent collectors up to self,
             starting from root of collection tree. """
@@ -327,6 +345,10 @@ class Collector(Node):
             return str(exc.args[0])
         return self._repr_failure_py(excinfo, style="short")
 
+    def _memocollect(self):
+        """ internal helper method to cache results of calling collect(). """
+        return self._memoizedcall('_collected', lambda: list(self.collect()))
+
     def _prunetraceback(self, excinfo):
         if hasattr(self, 'fspath'):
             path = self.fspath
diff --git a/_pytest/python.py b/_pytest/python.py
index 3276f16ae..b2ad05f8a 100644
--- a/_pytest/python.py
+++ b/_pytest/python.py
@@ -332,12 +332,8 @@ def transfer_markers(funcobj, cls, mod):
 
 class Module(pytest.File, PyCollector):
     """ Collector for test classes and functions. """
-    _obj = None
-
     def _getobj(self):
-        if self._obj is None:
-            self._obj = self._importtestmodule()
-        return _obj
+        return self._memoizedcall('_obj', self._importtestmodule)
 
     def collect(self):
         self.session.funcargmanager._parsefactories(self.obj, self.nodeid)
diff --git a/_pytest/runner.py b/_pytest/runner.py
index fb8366090..c774835de 100644
--- a/_pytest/runner.py
+++ b/_pytest/runner.py
@@ -244,7 +244,7 @@ class TeardownErrorReport(BaseReport):
         self.__dict__.update(extra)
 
 def pytest_make_collect_report(collector):
-    call = CallInfo(lambda: list(collector.collect()), "collect")
+    call = CallInfo(collector._memocollect, "memocollect")
     longrepr = None
     if not call.excinfo:
         outcome = "passed"