diff --git a/owners-common/src/main/java/com/googlesource/gerrit/owners/common/JgitWrapper.java b/owners-common/src/main/java/com/googlesource/gerrit/owners/common/JgitWrapper.java
index 9668af8..c1a7368 100644
--- a/owners-common/src/main/java/com/googlesource/gerrit/owners/common/JgitWrapper.java
+++ b/owners-common/src/main/java/com/googlesource/gerrit/owners/common/JgitWrapper.java
@@ -34,9 +34,14 @@
 
   public static Optional<byte[]> getBlobAsBytes(Repository repository, String revision, String path)
       throws IOException {
+    ObjectId objectId = repository.resolve(revision);
+    if (objectId == null) {
+      return Optional.empty();
+    }
+
     try (final TreeWalk w =
         TreeWalk.forPath(
-            repository, path, parseCommit(repository, repository.resolve(revision)).getTree())) {
+            repository, path, parseCommit(repository, objectId).getTree())) {
 
       return Optional.ofNullable(w)
           .filter(walk -> (walk.getRawMode(0) & TYPE_MASK) == TYPE_FILE)