diff --git a/bin/bitbake-worker b/bin/bitbake-worker
index eba9c562..04d75701 100755
--- a/bin/bitbake-worker
+++ b/bin/bitbake-worker
@@ -241,7 +241,7 @@ def fork_off_task(cfg, data, databuilder, workerdata, extraconfigdata, runtask):
             newsi = os.open(os.devnull, os.O_RDWR)
             os.dup2(newsi, sys.stdin.fileno())
 
-            if umask:
+            if umask is not None:
                 os.umask(umask)
 
             try: