diff --git a/src/mode/fdm/slice.js b/src/mode/fdm/slice.js
index 0fb06f3e..4897fc02 100644
--- a/src/mode/fdm/slice.js
+++ b/src/mode/fdm/slice.js
@@ -474,7 +474,7 @@
             if (!isSynth && !vaseMode) {
                 // sparse layers only present when non-vase mose and sparse % > 0
                 let lastType;
-                let promises = isConcurrent ? [] : undefined;
+                let promises = false && isConcurrent ? [] : undefined;
                 forSlices(0.5, promises ? 0.55 : 0.7, slice => {
                     let params = slice.params || process;
                     if (!params.sliceFillSparse) {