diff --git a/packages/timer/src/index.ts b/packages/timer/src/index.ts
index a10fb1a..8cfb7a5 100644
--- a/packages/timer/src/index.ts
+++ b/packages/timer/src/index.ts
@@ -2,6 +2,7 @@
 /// SPDX-FileCopyrightText: Copyright © 2016-2021 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
 
 import { preserves, Observe, floatValue, Turn, Ref } from "@syndicate-lang/core";
+import { QuasiValue as Q } from "@syndicate-lang/core";
 
 export message type PeriodicTick(intervalMS);
 export assertion type TimeLaterThan(deadlineMS);
@@ -19,36 +20,40 @@ export function sleep(ds: Ref, ms: number, cb: () => void): void {
 export function boot(ds: Ref) {
     spawn named 'timer/PeriodicTick' {
         at ds {
-            during Observe(PeriodicTick($intervalMS)) =>
-                spawn linked named (preserves`PeriodicTick(${intervalMS})`) {
-                    const thisFacet = Turn.activeFacet;
-                    thisFacet.preventInertCheck();
-                    const handle = setInterval(() => thisFacet.turn(() => {
-                        send message PeriodicTick(intervalMS);
-                    }), floatValue(intervalMS as any));
-                    on stop clearInterval(handle);
-                }
+            during Observe({
+                "pattern": :pattern PeriodicTick(\Q.lit($intervalMS)),
+                "observer": _,
+            }) => spawn linked named (preserves`PeriodicTick(${intervalMS})`) {
+                const thisFacet = Turn.activeFacet;
+                thisFacet.preventInertCheck();
+                const handle = setInterval(() => thisFacet.turn(() => {
+                    send message PeriodicTick(intervalMS);
+                }), floatValue(intervalMS));
+                on stop clearInterval(handle);
+            }
         }
     }
 
     spawn named 'timer/TimeLaterThan' {
         at ds {
-            during Observe(TimeLaterThan($deadlineMS)) =>
-                spawn linked named (preserves`TimeLaterThan(${deadlineMS})`) {
-                    const thisFacet = Turn.activeFacet;
-                    thisFacet.preventInertCheck();
-                    let delta = floatValue(deadlineMS as any) - (+(new Date()));
-                    let handle: any | null = setTimeout(() => thisFacet.turn(() => {
-                        handle = null;
-                        react {
-                            assert TimeLaterThan(deadlineMS);
-                        }
-                    }), delta);
-                    on stop if (handle) {
-                        clearTimeout(handle);
-                        handle = null;
+            during Observe({
+                "pattern": :pattern TimeLaterThan(\Q.lit($deadlineMS)),
+                "observer": _,
+            }) => spawn linked named (preserves`TimeLaterThan(${deadlineMS})`) {
+                const thisFacet = Turn.activeFacet;
+                thisFacet.preventInertCheck();
+                let delta = floatValue(deadlineMS) - (+(new Date()));
+                let handle: any | null = setTimeout(() => thisFacet.turn(() => {
+                    handle = null;
+                    react {
+                        assert TimeLaterThan(deadlineMS);
                     }
+                }), delta);
+                on stop if (handle) {
+                    clearTimeout(handle);
+                    handle = null;
                 }
+            }
         }
     }
 }