diff --git a/lms/djangoapps/certificates/tests/test_webview_views.py b/lms/djangoapps/certificates/tests/test_webview_views.py
index 7eff05d63d..830579ccef 100644
--- a/lms/djangoapps/certificates/tests/test_webview_views.py
+++ b/lms/djangoapps/certificates/tests/test_webview_views.py
@@ -694,6 +694,16 @@ class CertificatesViewsTests(ModuleStoreTestCase, EventTrackingTestCase):
         response = self.client.get(test_url)
         self.assertIn('invalid', response.content)
 
+    @override_settings(FEATURES=FEATURES_WITH_CERTS_ENABLED)
+    def test_render_html_view_non_int_user(self):
+        self._add_course_certificates(count=1, signatory_count=0)
+        test_url = get_certificate_url(
+            user_id="Good tests make good neighbors",
+            course_id=unicode(self.course.id)
+        )
+        response = self.client.get(test_url)
+        self.assertEqual(response.status_code, 404)
+
     @override_settings(FEATURES=FEATURES_WITH_CERTS_ENABLED)
     def test_render_html_view_invalid_user_certificate(self):
         self._add_course_certificates(count=1, signatory_count=0)
diff --git a/lms/djangoapps/certificates/views/webview.py b/lms/djangoapps/certificates/views/webview.py
index bd3a656548..381c2fa7ad 100644
--- a/lms/djangoapps/certificates/views/webview.py
+++ b/lms/djangoapps/certificates/views/webview.py
@@ -496,6 +496,11 @@ def render_html_view(request, user_id, course_id):
     This public view generates an HTML representation of the specified user and course
     If a certificate is not available, we display a "Sorry!" screen instead
     """
+    try:
+        user_id = int(user_id)
+    except ValueError:
+        raise Http404
+
     preview_mode = request.GET.get('preview', None)
     platform_name = microsite.get_value("platform_name", settings.PLATFORM_NAME)
     configuration = CertificateHtmlViewConfiguration.get_config()
@@ -506,6 +511,11 @@ def render_html_view(request, user_id, course_id):
 
     # Kick the user back to the "Invalid" screen if the feature is disabled
     if not has_html_certificates_enabled(course_id):
+        log.info(
+            "Invalid cert: HTML certificates disabled for %s. User id: %d",
+            course_id,
+            user_id,
+        )
         return render_to_response(invalid_template_path, context)
 
     # Load the course and user objects
@@ -515,12 +525,22 @@ def render_html_view(request, user_id, course_id):
         course = modulestore().get_course(course_key)
 
     # For any other expected exceptions, kick the user back to the "Invalid" screen
-    except (InvalidKeyError, ItemNotFoundError, User.DoesNotExist):
+    except (InvalidKeyError, ItemNotFoundError, User.DoesNotExist) as exception:
+        error_str = (
+            "Invalid cert: error finding course %s or user with id "
+            "%d. Specific error: %s"
+        )
+        log.info(error_str, course_id, user_id, str(exception))
         return render_to_response(invalid_template_path, context)
 
     # Load user's certificate
     user_certificate = _get_user_certificate(request, user, course_key, course, preview_mode)
     if not user_certificate:
+        log.info(
+            "Invalid cert: User %d does not have eligible cert for %s.",
+            user_id,
+            course_id,
+        )
         return render_to_response(invalid_template_path, context)
 
     # Get the active certificate configuration for this course
@@ -528,7 +548,13 @@ def render_html_view(request, user_id, course_id):
     # Passing in the 'preview' parameter, if specified, will return a configuration, if defined
     active_configuration = get_active_web_certificate(course, preview_mode)
     if active_configuration is None:
+        log.info(
+            "Invalid cert: course %s does not have an active configuration. User id: %d",
+            course_id,
+            user_id,
+        )
         return render_to_response(invalid_template_path, context)
+
     context['certificate_data'] = active_configuration
 
     # Append/Override the existing view context values with any mode-specific ConfigurationModel values