diff --git a/WDL/Error.py b/WDL/Error.py
index 091efae7..9e1a971a 100644
--- a/WDL/Error.py
+++ b/WDL/Error.py
@@ -234,8 +234,8 @@ def __init__(self, node: SourceNode, name: str) -> None:
         super().__init__(
             node,
             (
-                "Cannot call workflow {} because its calls don't supply all required inputs, "
-                "or it lacks an output section"
+                "Cannot call subworkflow {} because its own calls have missing required inputs, "
+                "and/or it lacks an output section"
             ).format(name),
         )