diff --git a/workflow/rules/sortmerna.rules b/workflow/rules/sortmerna.rules
index 3e384c6a53fdbc7b78a052230dc224480469d9cd..b7f5d5daa8875d5fac3f5a6be23bae5b5228f576 100755
--- a/workflow/rules/sortmerna.rules
+++ b/workflow/rules/sortmerna.rules
@@ -60,7 +60,7 @@ rule sortmerna:
         #get file extension
         if [[ ${{infiles[0]}} =~ \.gz$ ]]
         then
-            ext="gz"
+            ext=".gz"
         else
             ext=""
         fi