diff --git a/.dockstore.yml b/.dockstore.yml
index 41e282b6cd8..b18930ec2b2 100644
--- a/.dockstore.yml
+++ b/.dockstore.yml
@@ -79,6 +79,7 @@ workflows:
        branches:
          - master
          - ah_var_store
+         - rsa_sum_python
    - name: GvsRescatterCallsetInterval
      subclass: WDL
      primaryDescriptorPath: /scripts/variantstore/wdl/GvsRescatterCallsetInterval.wdl
diff --git a/scripts/variantstore/wdl/GvsExtractCallset.wdl b/scripts/variantstore/wdl/GvsExtractCallset.wdl
index a16849ddefc..9dff2054fc9 100644
--- a/scripts/variantstore/wdl/GvsExtractCallset.wdl
+++ b/scripts/variantstore/wdl/GvsExtractCallset.wdl
@@ -386,7 +386,7 @@ task SumBytes {
 
   command <<<
     set -e
-    echo "~{sep=" " file_sizes_bytes}" | tr " " "\n" | python -c "
+    echo "~{sep=" " file_sizes_bytes}" | tr " " "\n" | python3 -c "
     import sys;
     total_bytes = sum(float(i.strip()) for i in sys.stdin);
     total_mb = total_bytes/10**6;