diff --git a/src/main/clojure/cljs/closure.clj b/src/main/clojure/cljs/closure.clj
index b215573f6..a8d4a4757 100644
--- a/src/main/clojure/cljs/closure.clj
+++ b/src/main/clojure/cljs/closure.clj
@@ -1389,11 +1389,12 @@
         (let [source (first sources)]
           (recur
             (next sources)
-            (let [{:keys [provides source-url]} source]
-              (if (and provides source-url)
+            (let [{:keys [provides]} source
+                  url (or (:source-url source) (:url source))]
+              (if (and provides url)
                 (assoc relpaths
-                  (.getPath ^URL source-url)
-                  (util/ns->relpath (first provides) (util/ext source-url)))
+                  (.getPath ^URL url)
+                  (util/ns->relpath (first provides) (util/ext url)))
                 relpaths))
             (if-let [url (:url source)]
               (let [path (.getPath ^URL url)]
@@ -1410,19 +1411,19 @@
         (spit
           (io/file name)
           (sm/encode merged
-            {:preamble-line-count (+ (:preamble-line-count opts 0)
-                                     (:foreign-deps-line-count opts 0))
-             :lines (+ (:lineCount sm-json)
-                       (:preamble-line-count opts 0)
-                       (:foreign-deps-line-count opts 0)
-                       2)
-             :file name
-             :output-dir (util/output-directory opts)
-             :source-map (:source-map opts)
-             :source-map-path (:source-map-path opts)
-             :source-map-timestamp (:source-map-timestamp opts)
+            {:preamble-line-count     (+ (:preamble-line-count opts 0)
+                                        (:foreign-deps-line-count opts 0))
+             :lines                   (+ (:lineCount sm-json)
+                                        (:preamble-line-count opts 0)
+                                        (:foreign-deps-line-count opts 0)
+                                        2)
+             :file                    name
+             :output-dir              (util/output-directory opts)
+             :source-map              (:source-map opts)
+             :source-map-path         (:source-map-path opts)
+             :source-map-timestamp    (:source-map-timestamp opts)
              :source-map-pretty-print (:source-map-pretty-print opts)
-             :relpaths relpaths}))))))
+             :relpaths                relpaths}))))))
 
 (defn write-variable-maps [^Result result opts]
   (let [var-out (:closure-variable-map-out opts)]
diff --git a/src/test/cljs_build/adv_src_map/core.cljs b/src/test/cljs_build/adv_src_map/core.cljs
new file mode 100644
index 000000000..22cc32cab
--- /dev/null
+++ b/src/test/cljs_build/adv_src_map/core.cljs
@@ -0,0 +1,3 @@
+(ns adv-src-map.core)
+
+(.log js/console "Hello!" (first [1 2 3]))
\ No newline at end of file
diff --git a/src/test/clojure/cljs/build_api_tests.clj b/src/test/clojure/cljs/build_api_tests.clj
index e788c1ace..0edb2876a 100644
--- a/src/test/clojure/cljs/build_api_tests.clj
+++ b/src/test/clojure/cljs/build_api_tests.clj
@@ -840,3 +840,30 @@
       (.delete (io/file "package.json"))
       (test/delete-node-modules)
       (test/delete-out-files out))))
+
+#_(deftest test-advanced-source-maps
+  (testing "Test that the `sources` of the final merged source map matches the
+  one in the original Closure Compiler generated advanced source map"
+    (let [out (.getPath (io/file (test/tmp-dir) "adv-src-map"))]
+      (test/delete-out-files out)
+      (test/delete-node-modules)
+      (let [{:keys [inputs opts]} {:inputs (str (io/file "src" "test" "cljs_build"))
+                                   :opts   {:main               'cljs-3346-as-alias.core
+                                            :output-to          (.getPath (io/file out "main.js"))
+                                            :source-map         (.getPath (io/file out "main.js.map"))
+                                            :output-dir         out
+                                            :optimizations      :advanced
+                                            :closure-source-map true}}
+            cenv (env/default-compiler-env)]
+        (build/build (build/inputs (io/file inputs "adv_src_map/core.cljs")) opts cenv))
+      (let [cljs-src-map    (->> (io/file out "main.js.map") slurp json/read-str)
+            closure-src-map (->> (io/file out "main.js.map.closure") slurp json/read-str)]
+        (println (get closure-src-map "sources"))
+        (println (get cljs-src-map "sources")))
+      (test/delete-out-files out))))
+
+#_(comment
+
+  (clojure.test/test-vars [#'test-advanced-source-maps])
+
+  )
\ No newline at end of file