diff --git a/packages/core/src/skeleton.js b/packages/core/src/skeleton.js
index 6f40909..4794fb5 100644
--- a/packages/core/src/skeleton.js
+++ b/packages/core/src/skeleton.js
@@ -460,6 +460,19 @@ function isCompletelyConcrete(p) {
   return walk(p);
 }
 
+function withoutCaptures(p) {
+  function walk(p) {
+    if (Capture.isClassOf(p)) return walk(p.get(0));
+    if (Discard.isClassOf(p)) return p;
+
+    const cls = classOf(p);
+    if (cls === null) return p;
+    if (typeof cls === 'number') return p.map(walk);
+    return new Record(p.label, p.fields.map(walk));
+  }
+  return walk(p);
+}
+
 ///////////////////////////////////////////////////////////////////////////
 
 module.exports.EVENT_ADDED = EVENT_ADDED;
@@ -471,3 +484,4 @@ module.exports.analyzeAssertion = analyzeAssertion;
 module.exports.instantiateAssertion = instantiateAssertion;
 module.exports.match = match;
 module.exports.isCompletelyConcrete = isCompletelyConcrete;
+module.exports.withoutCaptures = withoutCaptures;
diff --git a/packages/syntax-server/src/job.js b/packages/syntax-server/src/job.js
index 1fd2229..7e48bfa 100644
--- a/packages/syntax-server/src/job.js
+++ b/packages/syntax-server/src/job.js
@@ -17,8 +17,9 @@ spawn named 'JobDispatcher' {
 
   during Observe(Observe(WorkItem($worker, $pattern, _))) {
     if (!Skeleton.isCompletelyConcrete(pattern)) {
-      on start addWorker(pattern, worker);
-      on stop removeWorker(pattern, worker);
+      const p = Skeleton.withoutCaptures(pattern);
+      on start addWorker(p, worker);
+      on stop removeWorker(p, worker);
     }
   }