diff --git a/tools/graphlan/export2graphlan/Snakefile b/tools/graphlan/export2graphlan/Snakefile
index 3da13bd9bdcb1693996b023d4836f643d3f4ee76..3377b9c8733be9a50134a5ae2d1740d3dbf5f8c3 100644
--- a/tools/graphlan/export2graphlan/Snakefile
+++ b/tools/graphlan/export2graphlan/Snakefile
@@ -5,7 +5,7 @@ rule export2graphlan:
     input:
         __export2graphlan_input
     output:
-        tree = __export2graphlan_output_tree
+        tree = __export2graphlan_output_tree,
         annot = __export2graphlan_output_annot
     params:
         exec_command = __export2graphlan_exec_command,