diff --git a/lisp/svg.el b/lisp/svg.el
index 7aadbc2359..45870e0bfe 100644
--- a/lisp/svg.el
+++ b/lisp/svg.el
@@ -154,9 +154,9 @@ svg-polyline
    (dom-node
     'polyline
     `((points . ,(mapconcat (lambda (pair)
-			      (format "%s %s" (car pair) (cdr pair)))
+			      (format "%s,%s" (car pair) (cdr pair)))
 			    points
-			    ", "))
+			    " "))
       ,@(svg--arguments svg args)))))
 
 (defun svg-polygon (svg points &rest args)
@@ -214,16 +214,17 @@ svg--encode-text
     (buffer-string)))
 
 (defun svg--append (svg node)
+  ;; id is expected to be unique.
   (let ((old (and (dom-attr node 'id)
 		  (dom-by-id svg
                              (concat "\\`" (regexp-quote (dom-attr node 'id))
                                      "\\'")))))
     (if old
-        ;; FIXME: This was (dom-set-attributes old (dom-attributes node))
-        ;; and got changed by commit f7ea7aa11f6211b5142bbcfc41c580d75485ca56
-        ;; without any explanation.
-	(setcdr (car old) (cdr node))
-      (dom-append-child svg node)))
+        ;; Remove old node. New node might be a different type.
+        (mapc (lambda (a)
+                  (dom-remove-node svg a))
+                old))
+    (dom-append-child svg node))
   (svg-possibly-update-image svg))
 
 (defun svg--image-data (image image-type datap)
@@ -311,7 +312,8 @@ svg-print
     (insert (format "<%s" (car dom)))
     (dolist (attr (nth 1 dom))
       ;; Ignore attributes that start with a colon.
-      (unless (= (aref (format "%s" (car attr)) 0) ?:)
+      (unless (or (= (aref (format "%s" (car attr)) 0) ?:)
+                  (null (cdr attr)))
         (insert (format " %s=\"%s\"" (car attr) (cdr attr)))))
     (insert ">")
     (dolist (elem (nthcdr 2 dom))