diff --git a/src/kiri-run/minion.js b/src/kiri-run/minion.js
index 18b5b2ee..98f2765d 100644
--- a/src/kiri-run/minion.js
+++ b/src/kiri-run/minion.js
@@ -61,16 +61,18 @@ const funcs = {
             reply({ seq, union: codec.encode([]) });
             return;
         }
+        let state = { zeros: [] };
         let polys = codec.decode(data.polys);
         let union = POLY.union(polys, data.minarea || 0, true);
-        reply({ seq, union: codec.encode(union) });
+        reply({ seq, union: codec.encode(union) }, state.zeros);
     },
 
     topShells: (data, seq) => {
         let top = codec.decode(data.top, {full: true});
         let {z, count, offset1, offsetN, fillOffset, opt} = data;
         kiri.driver.FDM.doTopShells(z, top, count, offset1, offsetN, fillOffset, opt);
-        reply({ seq, top: codec.encode(top, {full: true}) });
+        let state = { zeros: [] };
+        reply({ seq, top: codec.encode(top, {full: true}) }, state.zeros);
     },
 
     fill: (data, seq) => {
@@ -111,6 +113,7 @@ const funcs = {
         while (i < points.length) {
             realp[p++] = base.newPoint(points[i++], points[i++], points[i++]).round(3);
         }
+        let state = { zero: [] };
         let output = [];
         base.sliceZ(z, realp, {
             ...options,
@@ -120,7 +123,7 @@ const funcs = {
                 // lines do not pass codec properly (for now)
                 delete rec.lines;
             }
-            reply({ seq, output: codec.encode(output) });
+            reply({ seq, output: codec.encode(output) }, state.zeros);
         });
     },
 
diff --git a/src/kiri-run/worker.js b/src/kiri-run/worker.js
index 6fc0446e..184bf086 100644
--- a/src/kiri-run/worker.js
+++ b/src/kiri-run/worker.js
@@ -100,8 +100,9 @@ kiri.minions = {
             let polyper = Math.ceil(polys.length / concurrent);
             let running = 0;
             let union = [];
+            let state = { zeros: [] };
             let receiver = function(data) {
-                let polys = codec.decode(data.union);
+                let polys = codec.decode(data.union, state);
                 union.appendAll(polys);
                 if (--running === 0) {
                     resolve(POLY.union(union, minarea, true));
@@ -113,7 +114,7 @@ kiri.minions = {
                     cmd: "union",
                     minarea,
                     polys: codec.encode(polys.slice(i, i + polyper))
-                }, receiver);
+                }, receiver, state.zeros);
             }
         });
     },
@@ -124,9 +125,10 @@ kiri.minions = {
                 resolve(POLY.fillArea(polys, angle, spacing, [], minLen, maxLen));
                 return;
             }
+            const state = { zeros: [] };
             minwork.queue({
                 cmd: "fill",
-                polys: codec.encode(polys),
+                polys: codec.encode(polys, state),
                 angle, spacing, minLen, maxLen
             }, data => {
                 let arr = data.fill;
@@ -138,7 +140,7 @@ kiri.minions = {
                 }
                 output.appendAll(fill);
                 resolve(fill);
-            });
+            }, state.zeros);
         });
     },