diff --git a/notebook/nbextensions.py b/notebook/nbextensions.py
index 06fd313f1..71977833c 100644
--- a/notebook/nbextensions.py
+++ b/notebook/nbextensions.py
@@ -215,14 +215,19 @@ def install_nbextension(path, overwrite=False, symlink=False,
 def install_nbextension_python(package, overwrite=False, symlink=False,
                         user=False, sys_prefix=False, prefix=None, nbextensions_dir=None, logger=None):
     """Install an nbextension bundled in a Python package.
-    
+
+    Returns a list of installed/updated directories.
+
     See install_nbextension for parameter information."""
     m, nbexts = _get_nbextension_metadata(package)
     base_path = os.path.split(m.__file__)[0]
+
+    full_dests = []
+
     for nbext in nbexts:
         src = os.path.join(base_path, nbext['src'])
         dest = nbext['dest']
-        require = nbext['require']
+
         if logger:
             logger.info("Installing %s -> %s" % (src, dest))
         full_dest = install_nbextension(
@@ -231,8 +236,9 @@ def install_nbextension_python(package, overwrite=False, symlink=False,
             destination=dest, logger=logger
             )
         validate_nbextension_python(nbext, full_dest, logger)
+        full_dests.append(full_dest)
 
-
+    return full_dests
 
 def uninstall_nbextension(dest, require, user=False, sys_prefix=False, prefix=None, 
                           nbextensions_dir=None, logger=None):
@@ -379,16 +385,26 @@ def validate_nbextension(require, logger=None):
     
     return warnings
 
+
 def validate_nbextension_python(spec, full_dest, logger=None):
     """Assess the health of an installed nbextension
 
+    Returns a list of warnings.
+
     Parameters
     ----------
 
     spec : dict
-        A single entry of _jupyter_nbextension_paths()
+        A single entry of _jupyter_nbextension_paths():
+            [{
+                'section': 'notebook',
+                'src': 'mockextension',
+                'dest': '_mockdestination',
+                'require': '_mockdestination/index'
+            }]
     full_dest : str
-        The on-disk location of the installed nbextension
+        The on-disk location of the installed nbextension: this should end
+        with `nbextensions/<dest>`
     logger : Jupyter logger [optional]
         Logger instance to use
     """
@@ -403,7 +419,9 @@ def validate_nbextension_python(spec, full_dest, logger=None):
 
     require = spec.get("require", None)
     if require is not None:
-        require_path = os.path.join(full_dest, "{}.js".format(require))
+        require_path = os.path.join(
+            full_dest[0:-len(spec["dest"])],
+            "{}.js".format(require))
         if os.path.exists(require_path):
             infos.append("  {} require: {}".format(GREEN_OK, require_path))
         else:
@@ -418,7 +436,7 @@ def validate_nbextension_python(spec, full_dest, logger=None):
         else:
             logger.info("- Validating: {}".format(GREEN_OK))
 
-    return infos, warnings
+    return warnings
 
 
 #----------------------------------------------------------------------
diff --git a/notebook/serverextensions.py b/notebook/serverextensions.py
index a78cacfa7..13b8d0f01 100644
--- a/notebook/serverextensions.py
+++ b/notebook/serverextensions.py
@@ -85,6 +85,8 @@ def toggle_serverextension_python(import_name, enabled=None, parent=None,
 def validate_serverextension(import_name, logger=None):
     """Assess the health of an installed server extension
 
+    Returns a list of validation warnings.
+
     Parameters
     ----------
 
@@ -123,7 +125,7 @@ def validate_serverextension(import_name, logger=None):
         else:
             logger.info(post_mortem.format(import_name, "", GREEN_OK))
 
-    return not warnings
+    return warnings
 
 
 # ----------------------------------------------------------------------
diff --git a/notebook/tests/test_nbextensions.py b/notebook/tests/test_nbextensions.py
index 39d73f21c..a99790a46 100644
--- a/notebook/tests/test_nbextensions.py
+++ b/notebook/tests/test_nbextensions.py
@@ -24,7 +24,8 @@ from ipython_genutils.tempdir import TemporaryDirectory
 from notebook import nbextensions
 from notebook.nbextensions import (install_nbextension, check_nbextension,
     install_nbextension_python, uninstall_nbextension_python,
-    enable_nbextension_python, disable_nbextension_python, _get_config_dir
+    enable_nbextension_python, disable_nbextension_python, _get_config_dir,
+    validate_nbextension, validate_nbextension_python
 )
 
 from traitlets.config.manager import BaseJSONConfigManager
@@ -346,20 +347,26 @@ class TestInstallNBExtension(TestCase):
         
             with self.assertRaises(ValueError):
                 install_nbextension(zsrc, destination='foo')
-    
+
+    def _mock_extension_spec_meta(self, section='notebook'):
+        return {
+            'section': section,
+            'src': 'mockextension',
+            'dest': '_mockdestination',
+            'require': '_mockdestination/index'
+        }
+
     def _inject_mock_extension(self, section='notebook'):
         outer_file = __file__
+
+        meta = self._mock_extension_spec_meta(section)
+
         class mock():
             __file__ = outer_file
             
             @staticmethod
             def _jupyter_nbextension_paths():
-                return [{
-                    'section': section,
-                    'src': 'mockextension',
-                    'dest': '_mockdestination',
-                    'require': '_mockdestination/index'
-                }]
+                return [meta]
         
         import sys
         sys.modules['mockextension'] = mock
@@ -406,3 +413,27 @@ class TestInstallNBExtension(TestCase):
         cm = BaseJSONConfigManager(config_dir=config_dir)
         enabled = cm.get('notebook').get('load_extensions', {}).get('_mockdestination/index', False)
         assert not enabled
+
+    def test_nbextensionpy_validate(self):
+        self._inject_mock_extension('notebook')
+
+        paths = install_nbextension_python('mockextension')
+        enable_nbextension_python('mockextension', user=True)
+
+        meta = self._mock_extension_spec_meta()
+        warnings = validate_nbextension_python(meta, paths[0])
+        self.assertEqual([], warnings, warnings)
+
+    def test_nbextensionpy_validate_bad(self):
+        # Break the metadata (correct file will still be copied)
+        self._inject_mock_extension('notebook')
+
+        paths = install_nbextension_python('mockextension')
+        enable_nbextension_python('mockextension', user=True)
+
+        meta = self._mock_extension_spec_meta()
+        meta.update(require="bad-require")
+
+        warnings = validate_nbextension_python(meta, paths[0])
+
+        self.assertNotEqual([], warnings, warnings)