diff --git a/lib/galaxy_test/base/populators.py b/lib/galaxy_test/base/populators.py
index 25f9354f1c30..82afea738184 100644
--- a/lib/galaxy_test/base/populators.py
+++ b/lib/galaxy_test/base/populators.py
@@ -2212,8 +2212,8 @@ def setup_workflow_run(
             if inputs_by == "step_uuid":
                 workflow_request["inputs_by"] = "step_uuid"
         elif inputs_by == "url":
-            input_b64_1 = base64.b64encode("1 2 3".encode("utf-8")).decode("utf-8")
-            input_b64_2 = base64.b64encode("4 5 6".encode("utf-8")).decode("utf-8")
+            input_b64_1 = base64.b64encode("1 2 3").decode("utf-8")
+            input_b64_2 = base64.b64encode("4 5 6").decode("utf-8")
             inputs = {
                 "WorkflowInput1": {"src": "url", "url": f"base64://{input_b64_1}", "ext": "txt"},
                 "WorkflowInput2": {"src": "url", "url": f"base64://{input_b64_2}", "ext": "txt"},