diff --git a/gwcelery/tasks/external_skymaps.py b/gwcelery/tasks/external_skymaps.py
index fee761b16393794c4146fd02079446ccb9fa602b..20af785b3e00d616477aff67f632cfe28c943f5a 100644
--- a/gwcelery/tasks/external_skymaps.py
+++ b/gwcelery/tasks/external_skymaps.py
@@ -95,7 +95,7 @@ def combine_skymaps(skymapfilesbytes):
     trigger skymap and the LVC skymap and writes to a temporary output file. It
     then returns the contents of the file as a byte array.
     """
-    skymap1filebytes, skymap2filebytes = skymapbytes
+    skymap1filebytes, skymap2filebytes = skymapfilebytes
     with NamedTemporaryFile(mode='rb', suffix='.fits.gz') as combinedskymap, \
             NamedTemporaryFile(content=skymap1filebytes) as skymap1file, \
             NamedTemporaryFile(content=skymap2filebytes) as skymap2file, \