diff --git a/actions/apigroupismember.php b/actions/apigroupismember.php
index a822d18ddd..08348e97bd 100644
--- a/actions/apigroupismember.php
+++ b/actions/apigroupismember.php
@@ -92,7 +92,7 @@ class ApiGroupIsMemberAction extends ApiBareAuthAction
         }
 
         if (empty($this->group)) {
-            $this->clientError('Group not found!', 404, $this->format);
+            $this->clientError(_('Group not found!'), 404, $this->format);
             return false;
         }
 
diff --git a/actions/apigroupjoin.php b/actions/apigroupjoin.php
index ffda3986ff..b531d95015 100644
--- a/actions/apigroupjoin.php
+++ b/actions/apigroupjoin.php
@@ -101,7 +101,7 @@ class ApiGroupJoinAction extends ApiAuthAction
         }
 
         if (empty($this->group)) {
-            $this->clientError('Group not found!', 404, $this->format);
+            $this->clientError(_('Group not found!'), 404, $this->format);
             return false;
         }
 
diff --git a/actions/apigroupleave.php b/actions/apigroupleave.php
index 8665ea1aa8..514a3a557d 100644
--- a/actions/apigroupleave.php
+++ b/actions/apigroupleave.php
@@ -101,7 +101,7 @@ class ApiGroupLeaveAction extends ApiAuthAction
         }
 
         if (empty($this->group)) {
-            $this->clientError('Group not found!', 404, $this->format);
+            $this->clientError(_('Group not found!'), 404, $this->format);
             return false;
         }
 
diff --git a/actions/apigroupmembership.php b/actions/apigroupmembership.php
index d221a64183..dd2843161a 100644
--- a/actions/apigroupmembership.php
+++ b/actions/apigroupmembership.php
@@ -87,6 +87,11 @@ class ApiGroupMembershipAction extends ApiPrivateAuthAction
     {
         parent::handle($args);
 
+        if (empty($this->group)) {
+            $this->clientError(_('Group not found!'), 404, $this->format);
+            return false;
+        }
+
         // XXX: RSS and Atom
 
         switch($this->format) {
diff --git a/actions/apigroupshow.php b/actions/apigroupshow.php
index b745ff92f6..f9b960747b 100644
--- a/actions/apigroupshow.php
+++ b/actions/apigroupshow.php
@@ -87,7 +87,7 @@ class ApiGroupShowAction extends ApiPrivateAuthAction
 
         if (empty($this->group)) {
             $this->clientError(
-                'Group not found!',
+                _('Group not found!'),
                 404,
                 $this->format
             );
diff --git a/actions/apitimelinegroup.php b/actions/apitimelinegroup.php
index f25f6ba513..de13e7eb98 100644
--- a/actions/apitimelinegroup.php
+++ b/actions/apitimelinegroup.php
@@ -69,7 +69,6 @@ class ApiTimelineGroupAction extends ApiPrivateAuthAction
         parent::prepare($args);
 
         $this->group   = $this->getTargetGroup($this->arg('id'));
-        $this->notices = $this->getNotices();
 
         return true;
     }
@@ -87,6 +86,13 @@ class ApiTimelineGroupAction extends ApiPrivateAuthAction
     function handle($args)
     {
         parent::handle($args);
+
+        if (empty($this->group)) {
+            $this->clientError(_('Group not found!'), 404, $this->format);
+            return false;
+        }
+
+        $this->notices = $this->getNotices();
         $this->showTimeline();
     }