diff --git a/src/wp-includes/class-wp-xmlrpc-server.php b/src/wp-includes/class-wp-xmlrpc-server.php
index 10c593d2a4..53e1c792fb 100644
--- a/src/wp-includes/class-wp-xmlrpc-server.php
+++ b/src/wp-includes/class-wp-xmlrpc-server.php
@@ -2244,7 +2244,7 @@ class wp_xmlrpc_server extends IXR_Server {
 		$user_data = get_userdata( $user_id );
 
 		if ( ! $user_data )
-			return new IXR_Error( 404, __( 'Invalid user ID' ) );
+			return new IXR_Error( 404, __( 'Invalid user ID.' ) );
 
 		return $this->_prepare_user( $user_data, $fields );
 	}
@@ -3817,7 +3817,7 @@ class wp_xmlrpc_server extends IXR_Server {
 		do_action( 'xmlrpc_call', 'wp.getRevisions' );
 
 		if ( ! $post = get_post( $post_id ) )
-			return new IXR_Error( 404, __( 'Invalid post ID' ) );
+			return new IXR_Error( 404, __( 'Invalid post ID.' ) );
 
 		if ( ! current_user_can( 'edit_post', $post_id ) )
 			return new IXR_Error( 401, __( 'Sorry, you are not allowed to edit posts.' ) );
@@ -3878,13 +3878,13 @@ class wp_xmlrpc_server extends IXR_Server {
 		do_action( 'xmlrpc_call', 'wp.restoreRevision' );
 
 		if ( ! $revision = wp_get_post_revision( $revision_id ) )
-			return new IXR_Error( 404, __( 'Invalid post ID' ) );
+			return new IXR_Error( 404, __( 'Invalid post ID.' ) );
 
 		if ( wp_is_post_autosave( $revision ) )
-			return new IXR_Error( 404, __( 'Invalid post ID' ) );
+			return new IXR_Error( 404, __( 'Invalid post ID.' ) );
 
 		if ( ! $post = get_post( $revision->post_parent ) )
-			return new IXR_Error( 404, __( 'Invalid post ID' ) );
+			return new IXR_Error( 404, __( 'Invalid post ID.' ) );
 
 		if ( ! current_user_can( 'edit_post', $revision->post_parent ) )
 			return new IXR_Error( 401, __( 'Sorry, you cannot edit this post.' ) );
diff --git a/src/wp-includes/post-formats.php b/src/wp-includes/post-formats.php
index 94a38581c5..3a4e60c367 100644
--- a/src/wp-includes/post-formats.php
+++ b/src/wp-includes/post-formats.php
@@ -65,7 +65,7 @@ function set_post_format( $post, $format ) {
 	$post = get_post( $post );
 
 	if ( empty( $post ) )
-		return new WP_Error( 'invalid_post', __( 'Invalid post' ) );
+		return new WP_Error( 'invalid_post', __( 'Invalid post.' ) );
 
 	if ( ! empty( $format ) ) {
 		$format = sanitize_key( $format );
diff --git a/src/wp-includes/revision.php b/src/wp-includes/revision.php
index 310461211a..9d439a20eb 100644
--- a/src/wp-includes/revision.php
+++ b/src/wp-includes/revision.php
@@ -260,7 +260,7 @@ function _wp_put_post_revision( $post = null, $autosave = false ) {
 		$post = get_post($post, ARRAY_A);
 
 	if ( ! $post || empty($post['ID']) )
-		return new WP_Error( 'invalid_post', __( 'Invalid post ID' ) );
+		return new WP_Error( 'invalid_post', __( 'Invalid post ID.' ) );
 
 	if ( isset($post['post_type']) && 'revision' == $post['post_type'] )
 		return new WP_Error( 'post_type', __( 'Cannot create a revision of a revision' ) );