diff --git a/mozilla/webtools/bugzilla/.bzrrev b/mozilla/webtools/bugzilla/.bzrrev
index 327f0b34656..457d6cf3307 100644
--- a/mozilla/webtools/bugzilla/.bzrrev
+++ b/mozilla/webtools/bugzilla/.bzrrev
@@ -1 +1 @@
-7807
\ No newline at end of file
+7808
\ No newline at end of file
diff --git a/mozilla/webtools/bugzilla/Bugzilla/Bug.pm b/mozilla/webtools/bugzilla/Bugzilla/Bug.pm
index beafcfa8c3f..f3d635344b7 100644
--- a/mozilla/webtools/bugzilla/Bugzilla/Bug.pm
+++ b/mozilla/webtools/bugzilla/Bugzilla/Bug.pm
@@ -1641,11 +1641,14 @@ sub _check_groups {
 
         # First check all the groups they chose to set.
         foreach my $name (@$group_names) {
-            # We don't want to expose the existence or non-existence of groups,
-            # so instead of doing check(), we just do "next" on an invalid
-            # group.
-            my $group = new Bugzilla::Group({ name => $name }) or next;
-            next if !$product->group_is_settable($group);
+            my $group = Bugzilla::Group->check(
+                { name => $name, product => $product,
+                  _error => 'group_restriction_not_allowed' });
+
+            if (!$product->group_is_settable($group)) {
+                ThrowUserError('group_restriction_not_allowed',
+                               { name => $name, product => $product });
+            }
             $add_groups{$group->id} = $group;
         }
     }
diff --git a/mozilla/webtools/bugzilla/Bugzilla/WebService/Bug.pm b/mozilla/webtools/bugzilla/Bugzilla/WebService/Bug.pm
index 582a9ce9167..73310428639 100644
--- a/mozilla/webtools/bugzilla/Bugzilla/WebService/Bug.pm
+++ b/mozilla/webtools/bugzilla/Bugzilla/WebService/Bug.pm
@@ -2267,9 +2267,8 @@ is private, otherwise it is assumed to be public.
 =item C<groups> (array) - An array of group names to put this
 bug into. You can see valid group names on the Permissions
 tab of the Preferences screen, or, if you are an administrator,
-in the Groups control panel. Note that invalid group names or
-groups that the bug can't be restricted to are silently ignored. If
-you don't specify this argument, then a bug will be added into
+in the Groups control panel.
+If you don't specify this argument, then the bug will be added into
 all the groups that are set as being "Default" for this product. (If
 you want to avoid that, you should specify C<groups> as an empty array.)
 
@@ -2330,6 +2329,11 @@ You didn't specify a summary for the bug.
 You specified values in the C<blocks> or C<depends_on> fields
 that would cause a circular dependency between bugs.
 
+=item 120 (Group Restriction Denied)
+
+You tried to restrict the bug to a group which does not exist, or which
+you cannot use with this product.
+
 =item 504 (Invalid User)
 
 Either the QA Contact, Assignee, or CC lists have some invalid user
@@ -2346,7 +2350,9 @@ B<Required>, due to a bug in Bugzilla.
 
 =item The C<groups> argument was added in Bugzilla B<4.0>. Before
 Bugzilla 4.0, bugs were only added into Mandatory groups by this
-method.
+method. Since Bugzilla B<4.0.2>, passing an illegal group name will
+throw an error. In Bugzilla 4.0 and 4.0.1, illegal group names were
+silently ignored.
 
 =item The C<comment_is_private> argument was added in Bugzilla B<4.0>.
 Before Bugzilla 4.0, you had to use the undocumented C<commentprivacy>
diff --git a/mozilla/webtools/bugzilla/Bugzilla/WebService/Constants.pm b/mozilla/webtools/bugzilla/Bugzilla/WebService/Constants.pm
index a1063864f6b..cb518b0bd68 100644
--- a/mozilla/webtools/bugzilla/Bugzilla/WebService/Constants.pm
+++ b/mozilla/webtools/bugzilla/Bugzilla/WebService/Constants.pm
@@ -111,6 +111,7 @@ use constant WS_ERROR_CODE => {
     # Bug-related group errors
     group_change_denied => 120,
     group_invalid_restriction => 120,
+    group_restriction_not_allowed => 120,
     # Status/Resolution errors
     missing_resolution => 121,
     resolution_not_allowed => 122,
diff --git a/mozilla/webtools/bugzilla/template/en/default/global/user-error.html.tmpl b/mozilla/webtools/bugzilla/template/en/default/global/user-error.html.tmpl
index cda3d2e5dbd..1dd747f30a2 100644
--- a/mozilla/webtools/bugzilla/template/en/default/global/user-error.html.tmpl
+++ b/mozilla/webtools/bugzilla/template/en/default/global/user-error.html.tmpl
@@ -766,6 +766,13 @@
     '[% product FILTER html %]' product can not be restricted to
     that group.
 
+  [% ELSIF error == "group_restriction_not_allowed" %]
+    [% title = "Group Restriction Not Allowed" %]
+    You tried to restrict [% terms.abug %] to the "[% name FILTER html %]"
+    group, but either this group does not exist, or you are not allowed
+    to restrict [% terms.bugs %] to this group in the "[% product.name FILTER html %]"
+    product.
+
   [% ELSIF error == "group_not_specified" %]
     [% title = "Group not specified" %]
     No group was specified.