diff --git a/chronos/asyncmacro2.nim b/chronos/asyncmacro2.nim
index 02703ea..2978ba5 100644
--- a/chronos/asyncmacro2.nim
+++ b/chronos/asyncmacro2.nim
@@ -30,7 +30,7 @@ template createCb(retFutureSym, iteratorNameSym,
 
   var nameIterVar = iteratorNameSym
   {.push stackTrace: off.}
-  proc identName(udata: pointer = nil) {.closure.} =
+  proc identName(udata: pointer = nil) {.closure, gcsafe.} =
     try:
       if not(nameIterVar.finished()):
         var next = nameIterVar()
@@ -48,7 +48,7 @@ template createCb(retFutureSym, iteratorNameSym,
         else:
           {.gcsafe.}:
             {.push hint[ConvFromXtoItselfNotNeeded]: off.}
-            next.callback = CallbackFunc(identName)
+            next.callback = identName
             {.pop.}
     except CancelledError:
       retFutureSym.cancel()
diff --git a/tests/testsync.nim b/tests/testsync.nim
index 56c6a77..3f70885 100644
--- a/tests/testsync.nim
+++ b/tests/testsync.nim
@@ -11,8 +11,8 @@ import ../chronos
 when defined(nimHasUsed): {.used.}
 
 suite "Asynchronous sync primitives test suite":
-  var testLockResult = ""
-  var testEventResult = ""
+  var testLockResult {.threadvar.}: string
+  var testEventResult {.threadvar.}: string
   var testQueue1Result = 0
   var testQueue2Result = 0
   var testQueue3Result = 0