diff --git a/src/lambdaisland/hiccup.clj b/src/lambdaisland/hiccup.clj
index 481dfc4..eac6f90 100644
--- a/src/lambdaisland/hiccup.clj
+++ b/src/lambdaisland/hiccup.clj
@@ -43,7 +43,8 @@
                              (into {} (filter val m))
                              {})
                     :content (enlive/flatmap #(nodify % opts) (if (attr-map? m) ms more))}
-              node (if id (assoc-in node [:attrs :id] id) node)
+              node (if (and id (not (contains? (:attrs node) :id))) 
+                     (assoc-in node [:attrs :id] id) node)
               node (if (seq classes)
                      (update-in node
                                 [:attrs :class]