diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad1bff2..07a2e8a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## [Unreleased]
 
 ### Added
+* PR #13 copy with preconditions by @rfb.
 
 ### Changed
 
diff --git a/src/clj_gcloud/storage.clj b/src/clj_gcloud/storage.clj
index ea1538b..3fd03c7 100644
--- a/src/clj_gcloud/storage.clj
+++ b/src/clj_gcloud/storage.clj
@@ -105,9 +105,23 @@
     (.build builder)))
 
 (defn copy
-  [^Storage storage ^BlobId source-blob-id ^BlobId target-blob-id]
-  (-> (.copy storage (Storage$CopyRequest/of source-blob-id target-blob-id))
-      (.getResult)))
+  ([storage source-blob-id target-blob-id]
+   (copy storage source-blob-id target-blob-id nil))
+  ([^Storage storage ^BlobId source-blob-id ^BlobId target-blob-id options]
+   (let [cr (if (:with-precondition options)
+              ;; Copy blobs within cloud storage using preconditions recommended in Google Cloud Storage guides
+              ;; See: https://cloud.google.com/storage/docs/copying-renaming-moving-objects#storage-copy-object-java
+              (let [precondition (if-let [target (.get storage target-blob-id)]
+                                   (Storage$BlobTargetOption/generationMatch (.getGeneration target))
+                                   (Storage$BlobTargetOption/doesNotExist))
+                    ^Iterable target-opts (into-array Storage$BlobTargetOption [precondition])]
+                (-> (Storage$CopyRequest/newBuilder)
+                    (.setSource source-blob-id)
+                    (.setTarget target-blob-id target-opts)
+                    .build))
+              (Storage$CopyRequest/of source-blob-id target-blob-id))]
+     (-> (.copy storage cr)
+         (.getResult)))))
 
 (defn create-blob
   [^Storage storage ^BlobInfo blob-info]
@@ -229,5 +243,10 @@
    Usage :
    (download-file-from-storage storage-client 'gs://mybucket/myfolder/.../myfile' 'mylocalfile')"
   [^Storage storage source-gs-uri dest-local-path & _options]
-  (let [blob (->> source-gs-uri ->blob-id (get-blob storage))]
-    (.downloadTo blob (Paths/get dest-local-path (make-array String 0)) (into-array Blob$BlobSourceOption []))))
+  (let [^Blob blob (->> source-gs-uri ->blob-id (get-blob storage))
+        path (Paths/get dest-local-path (make-array String 0))
+        ;; this resolves reflection but it's pretty ugly:
+        ;; ^"[Lcom.google.cloud.storage.Blob$BlobSourceOption;" opts (into-array Blob$BlobSourceOption [])
+        ;; for now skip it, since we pass no options anyway
+        ]
+    (.downloadTo blob path)))
diff --git a/test/clj_gcloud/storage_test.clj b/test/clj_gcloud/storage_test.clj
index 5fb8388..584e19a 100644
--- a/test/clj_gcloud/storage_test.clj
+++ b/test/clj_gcloud/storage_test.clj
@@ -58,4 +58,3 @@
         (is (delete-blob *storage* (.getBlobId blob)))
         (is (= 0 (count (ls *storage* dest-uri)))))
       (.delete tmp))))
-