diff --git a/pkg/codegen/schema/schema.go b/pkg/codegen/schema/schema.go
index 41759a1659d8..d7d3fd6d998e 100644
--- a/pkg/codegen/schema/schema.go
+++ b/pkg/codegen/schema/schema.go
@@ -1724,6 +1724,11 @@ func (funcSpec FunctionSpec) MarshalFunctionSpec() map[string]interface{} {
 		}
 	}
 
+	// for backward-compat when we only specify the outputs object of the function
+	if funcSpec.ReturnType == nil && funcSpec.Outputs != nil {
+		data["outputs"] = funcSpec.Outputs
+	}
+
 	if funcSpec.DeprecationMessage != "" {
 		data["deprecationMessage"] = funcSpec.DeprecationMessage
 	}