diff --git a/lib/SILOptimizer/Mandatory/OptimizeHopToExecutor.cpp b/lib/SILOptimizer/Mandatory/OptimizeHopToExecutor.cpp
index 2aba1c3530537..af8d80761993b 100644
--- a/lib/SILOptimizer/Mandatory/OptimizeHopToExecutor.cpp
+++ b/lib/SILOptimizer/Mandatory/OptimizeHopToExecutor.cpp
@@ -196,10 +196,30 @@ void OptimizeHopToExecutor::solveDataflowBackward() {
   } while (changed);
 }
 
+bool fixme_isCallerIsoInheriting(FullApplySite FAS) {
+  if (FAS.isCallerIsolationInheriting())
+    return true;
+
+  auto actorIsolation = FAS.getActorIsolation();
+  //  llvm::dbgs() << "JQ: FAS actor iso:\n";
+  //  actorIsolation->dump();
+  if (actorIsolation->getKind() == ActorIsolation::Unspecified) {
+    // FIXME: handle closures that inherit the caller's isolation correctly
+    auto calleSubsTy = FAS.getSubstCalleeType();
+    auto implicitIsoParam = calleSubsTy->maybeGetIsolatedParameter();
+    //    llvm::dbgs() << "JQ: FAS imp iso param:\n";
+    //    implicitIsoParam->dump();
+    return implicitIsoParam.has_value();
+  }
+
+  return false;
+}
+
 /// Returns true if \p inst is a suspension point or an async call.
 static bool isSuspensionPoint(SILInstruction *inst) {
   if (auto applySite = FullApplySite::isa(inst)) {
-    if (applySite.isAsync() && !applySite.isCallerIsolationInheriting())
+    //    if (applySite.isAsync() && !applySite.isCallerIsolationInheriting())
+    if (applySite.isAsync() && !fixme_isCallerIsoInheriting(applySite))
       return true;
     return false;
   }
@@ -392,7 +412,10 @@ bool OptimizeHopToExecutor::needsExecutor(SILInstruction *inst) {
   // executors since caller isolation inheriting functions do not hop in their
   // prologue.
   if (auto fas = FullApplySite::isa(inst);
-      fas && fas.isAsync() && fas.isCallerIsolationInheriting()) {
+      fas && fas.isAsync() &&
+      fixme_isCallerIsoInheriting(fas)
+//      fas.isCallerIsolationInheriting()
+      ) {
     return true;
   }