diff --git a/setup.py b/setup.py
index 9a1a0f8b4941b8ac3384859de89a95f1d164203c..62f842ca0fb5429dfb185403b2391ccc2a8ed2a7 100644
--- a/setup.py
+++ b/setup.py
@@ -27,7 +27,9 @@ def get_version_from_file():
 def prepare_version():
     version = os.getenv("BUILD_TAG", '')
 
-    if version.startswith('v'):
+    if not version:
+        version = get_version_from_file()
+    elif version.startswith('v'):
         # release tag version, e.g. v0.9.0
         version = version[1:]
     else: