diff --git a/packages/swingset-liveslots/tools/fakeVirtualSupport.js b/packages/swingset-liveslots/tools/fakeVirtualSupport.js
index 6beadaac778a..ea6998e74e9b 100644
--- a/packages/swingset-liveslots/tools/fakeVirtualSupport.js
+++ b/packages/swingset-liveslots/tools/fakeVirtualSupport.js
@@ -169,7 +169,7 @@ export function makeFakeLiveSlotsStuff(options = {}) {
 
   function requiredValForSlot(slot) {
     const val = getValForSlot(slot);
-    assert(val, `no value for ${slot}`);
+    assert(val, `${slot} must have a value`);
     return val;
   }