diff --git a/examples/compiled/arc_radial.png b/examples/compiled/arc_radial.png
index dcb6398753..f111f131cb 100644
Binary files a/examples/compiled/arc_radial.png and b/examples/compiled/arc_radial.png differ
diff --git a/examples/compiled/arc_radial.vg.json b/examples/compiled/arc_radial.vg.json
index 8a23181fe6..83b164d48c 100644
--- a/examples/compiled/arc_radial.vg.json
+++ b/examples/compiled/arc_radial.vg.json
@@ -34,10 +34,7 @@
           "type": "stack",
           "groupby": [],
           "field": "data",
-          "sort": {
-            "field": ["data", "data"],
-            "order": ["ascending", "ascending"]
-          },
+          "sort": {"field": ["data"], "order": ["ascending"]},
           "as": ["data_start", "data_end"],
           "offset": "zero"
         },
diff --git a/examples/compiled/layer_arc_label.png b/examples/compiled/layer_arc_label.png
index 450c9d1817..0192b9d20b 100644
Binary files a/examples/compiled/layer_arc_label.png and b/examples/compiled/layer_arc_label.png differ
diff --git a/examples/compiled/layer_arc_label.vg.json b/examples/compiled/layer_arc_label.vg.json
index 558ba6bfe2..6cf4119997 100644
--- a/examples/compiled/layer_arc_label.vg.json
+++ b/examples/compiled/layer_arc_label.vg.json
@@ -44,10 +44,7 @@
           "type": "stack",
           "groupby": [],
           "field": "value",
-          "sort": {
-            "field": ["category", "category"],
-            "order": ["ascending", "ascending"]
-          },
+          "sort": {"field": ["category"], "order": ["ascending"]},
           "as": ["value_start", "value_end"],
           "offset": "zero"
         },
diff --git a/src/compile/data/stack.ts b/src/compile/data/stack.ts
index 184f85957e..553bba2279 100644
--- a/src/compile/data/stack.ts
+++ b/src/compile/data/stack.ts
@@ -146,8 +146,10 @@ export class StackNode extends DataFlowNode {
       // FIXME is the default here correct for binned fields?
       sort = stackby.reduce(
         (s, field) => {
-          s.field.push(field);
-          s.order.push(sortOrder);
+          if (!s.field.includes(field)) {
+            s.field.push(field);
+            s.order.push(sortOrder);
+          }
           return s;
         },
         {field: [], order: []}