diff --git a/bitbake/lib/bb/siggen.py b/bitbake/lib/bb/siggen.py
index 40085b9c54..542bbb9d13 100644
--- a/bitbake/lib/bb/siggen.py
+++ b/bitbake/lib/bb/siggen.py
@@ -564,7 +564,8 @@ def calc_taskhash(sigdata):
         data = data + sigdata['runtaskhashes'][dep]
 
     for c in sigdata['file_checksum_values']:
-        data = data + c[1]
+        if c[1]:
+            data = data + c[1]
 
     if 'taint' in sigdata:
         if 'nostamp:' in sigdata['taint']: