diff --git a/src/compile.cpp b/src/compile.cpp
index 48ab0aebeb..b1f5e0111a 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -6254,7 +6254,7 @@ class MyProcessor: public Processor {
       collect(t, Heap::MinorCollection);
     }
 
-    return visitor.trace;
+    return visitor.trace ? visitor.trace : makeArray(t, 0);
   }
 
   virtual void initialize(BootImage* image, uint8_t* code, unsigned capacity) {
diff --git a/src/posix.cpp b/src/posix.cpp
index b2b3800eee..fd45942ec5 100644
--- a/src/posix.cpp
+++ b/src/posix.cpp
@@ -628,13 +628,16 @@ class MySystem: public System {
     visitTarget = target;
 
     int rv = pthread_kill(target->thread, VisitSignal);
-    expect(this, rv == 0);
 
-    while (visitTarget) visitLock->wait(t, 0);
+    if (rv == 0) {
+      while (visitTarget) visitLock->wait(t, 0);
 
-    threadVisitor = 0;
+      threadVisitor = 0;
 
-    return 0;
+      return 0;
+    } else {
+      return -1;
+    }
   }
 
   virtual uint64_t call(void* function, uintptr_t* arguments, uint8_t* types,