diff --git a/common/lib/xmodule/xmodule/x_module.py b/common/lib/xmodule/xmodule/x_module.py
index 92776eabd8..709d81046e 100644
--- a/common/lib/xmodule/xmodule/x_module.py
+++ b/common/lib/xmodule/xmodule/x_module.py
@@ -191,6 +191,26 @@ class XModuleMixin(XBlockMixin):
         default=None
     )
 
+    def __init__(self, *args, **kwargs):
+        self.xmodule_runtime = None
+        super(XModuleMixin, self).__init__(*args, **kwargs)
+
+    @property
+    def runtime(self):
+        # Handle XModule backwards compatibility. If this is a pure
+        # XBlock, and it has an xmodule_runtime defined, then we're in
+        # an XModule context, not an XModuleDescriptor context,
+        # so we should use the xmodule_runtime (ModuleSystem) as the runtime.
+        if (not isinstance(self, (XModule, XModuleDescriptor)) and
+            self.xmodule_runtime is not None):
+            return self.xmodule_runtime
+        return self._runtime
+
+    @runtime.setter
+    def runtime(self, value):
+        self._runtime = value
+
+
     @property
     def system(self):
         """
@@ -1168,9 +1188,8 @@ class DescriptorSystem(MetricsMixin, ConfigurableFragmentWrapper, Runtime):  # p
             return super(DescriptorSystem, self).render(block, view_name, context)
 
     def handler_url(self, block, handler_name, suffix='', query='', thirdparty=False):
-        xmodule_runtime = getattr(block, 'xmodule_runtime', None)
-        if xmodule_runtime is not None:
-            return xmodule_runtime.handler_url(block, handler_name, suffix, query, thirdparty)
+        if block.xmodule_runtime is not None:
+            return block.xmodule_runtime.handler_url(block, handler_name, suffix, query, thirdparty)
         else:
             # Currently, Modulestore is responsible for instantiating DescriptorSystems
             # This means that LMS/CMS don't have a way to define a subclass of DescriptorSystem
@@ -1182,9 +1201,8 @@ class DescriptorSystem(MetricsMixin, ConfigurableFragmentWrapper, Runtime):  # p
         """
         See :meth:`xblock.runtime.Runtime:local_resource_url` for documentation.
         """
-        xmodule_runtime = getattr(block, 'xmodule_runtime', None)
-        if xmodule_runtime is not None:
-            return xmodule_runtime.local_resource_url(block, uri)
+        if block.xmodule_runtime is not None:
+            return block.xmodule_runtime.local_resource_url(block, uri)
         else:
             # Currently, Modulestore is responsible for instantiating DescriptorSystems
             # This means that LMS/CMS don't have a way to define a subclass of DescriptorSystem
@@ -1202,9 +1220,8 @@ class DescriptorSystem(MetricsMixin, ConfigurableFragmentWrapper, Runtime):  # p
         """
         See :meth:`xblock.runtime.Runtime:publish` for documentation.
         """
-        xmodule_runtime = getattr(block, 'xmodule_runtime', None)
-        if xmodule_runtime is not None:
-            return xmodule_runtime.publish(block, event_type, event)
+        if block.xmodule_runtime is not None:
+            return block.xmodule_runtime.publish(block, event_type, event)
 
     def add_block_as_child_node(self, block, node):
         child = etree.SubElement(node, "unknown")
diff --git a/requirements/edx/github.txt b/requirements/edx/github.txt
index c12c8293d9..3b40143eef 100644
--- a/requirements/edx/github.txt
+++ b/requirements/edx/github.txt
@@ -20,7 +20,7 @@
 -e git+https://github.com/pmitros/django-pyfs.git@d175715e0fe3367ec0f1ee429c242d603f6e8b10#egg=djpyfs
 
 # Our libraries:
--e git+https://github.com/edx/XBlock.git@81a6d713c98d4914af96a0ca624ee7fa4903625e#egg=XBlock
+-e git+https://github.com/edx/XBlock.git@246811773c67a84fdb17614a8e9f7ec7b1890574#egg=XBlock
 -e git+https://github.com/edx/codejail.git@66dd5a45e5072666ff9a70c768576e9ffd1daa4b#egg=codejail
 -e git+https://github.com/edx/diff-cover.git@v0.5.0#egg=diff_cover
 -e git+https://github.com/edx/js-test-tool.git@v0.1.5#egg=js_test_tool