diff --git a/host/commands/assemble_cvd/super_image_mixer.cc b/host/commands/assemble_cvd/super_image_mixer.cc
index 2081af4..b2ec8c2 100644
--- a/host/commands/assemble_cvd/super_image_mixer.cc
+++ b/host/commands/assemble_cvd/super_image_mixer.cc
@@ -43,6 +43,9 @@
       continue;
     }
     std::string expected_substr = "target_files-" + file_iter.second.build_id + ".zip";
+    if (expected_substr.size() > file_iter.first.size()) {
+      continue;
+    }
     auto expected_pos = file_iter.first.size() - expected_substr.size();
     if (file_iter.first.rfind(expected_substr) == expected_pos) {
       return file_iter.first;