diff --git a/lib/spack/spack/fetch_strategy.py b/lib/spack/spack/fetch_strategy.py
index 73083a0f5ab..27fb38b7a6b 100644
--- a/lib/spack/spack/fetch_strategy.py
+++ b/lib/spack/spack/fetch_strategy.py
@@ -216,7 +216,7 @@ def fetch(self):
 
         if not self.archive_file:
             raise FailedDownloadError(self.url)
-        else:
+        elif self.digest:
             shutil.copy(self.archive_file, spack.cache_path)