diff --git a/lib/system/orc.nim b/lib/system/orc.nim
index 6273e1a216eb..f9f5cd81fc68 100644
--- a/lib/system/orc.nim
+++ b/lib/system/orc.nim
@@ -79,10 +79,12 @@ proc trace(s: Cell; desc: PNimTypeV2; j: var GcEnv) {.inline.} =
     var p = s +! sizeof(RefHeader)
     cast[TraceProc](desc.traceImpl)(p, addr(j))
 
+include threadids
+
 when logOrc:
   proc writeCell(msg: cstring; s: Cell; desc: PNimTypeV2) =
-    cfprintf(cstderr, "%s %s %ld root index: %ld; RC: %ld; color: %ld\n",
-      msg, desc.name, s.refId, s.rootIdx, s.rc shr rcShift, s.color)
+    cfprintf(cstderr, "%s %s %ld root index: %ld; RC: %ld; color: %ld; thread: %ld\n",
+      msg, desc.name, s.refId, s.rootIdx, s.rc shr rcShift, s.color, getThreadId())
 
 proc free(s: Cell; desc: PNimTypeV2) {.inline.} =
   when traceCollector:
@@ -419,6 +421,7 @@ proc registerCycle(s: Cell; desc: PNimTypeV2) =
 proc GC_runOrc* =
   ## Forces a cycle collection pass.
   collectCycles()
+  orcAssert roots.len == 0, "roots not empty!"
 
 proc GC_enableOrc*() =
   ## Enables the cycle collector subsystem of `--gc:orc`. This is a `--gc:orc`
diff --git a/lib/system/threadids.nim b/lib/system/threadids.nim
new file mode 100644
index 000000000000..3a6eadcbbbc8
--- /dev/null
+++ b/lib/system/threadids.nim
@@ -0,0 +1,103 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2020 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+# we need to cache current threadId to not perform syscall all the time
+var threadId {.threadvar.}: int
+
+when defined(windows):
+  proc getCurrentThreadId(): int32 {.
+    stdcall, dynlib: "kernel32", importc: "GetCurrentThreadId".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(getCurrentThreadId())
+    result = threadId
+
+elif defined(linux):
+  proc syscall(arg: clong): clong {.varargs, importc: "syscall", header: "<unistd.h>".}
+  when defined(amd64):
+    const NR_gettid = clong(186)
+  else:
+    var NR_gettid {.importc: "__NR_gettid", header: "<sys/syscall.h>".}: clong
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(syscall(NR_gettid))
+    result = threadId
+
+elif defined(dragonfly):
+  proc lwp_gettid(): int32 {.importc, header: "unistd.h".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(lwp_gettid())
+    result = threadId
+
+elif defined(openbsd):
+  proc getthrid(): int32 {.importc: "getthrid", header: "<unistd.h>".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(getthrid())
+    result = threadId
+
+elif defined(netbsd):
+  proc lwp_self(): int32 {.importc: "_lwp_self", header: "<lwp.h>".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(lwp_self())
+    result = threadId
+
+elif defined(freebsd):
+  proc syscall(arg: cint, arg0: ptr cint): cint {.varargs, importc: "syscall", header: "<unistd.h>".}
+  var SYS_thr_self {.importc:"SYS_thr_self", header:"<sys/syscall.h>".}: cint
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    var tid = 0.cint
+    if threadId == 0:
+      discard syscall(SYS_thr_self, addr tid)
+      threadId = tid
+    result = threadId
+
+elif defined(macosx):
+  proc syscall(arg: cint): cint {.varargs, importc: "syscall", header: "<unistd.h>".}
+  var SYS_thread_selfid {.importc:"SYS_thread_selfid", header:"<sys/syscall.h>".}: cint
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(syscall(SYS_thread_selfid))
+    result = threadId
+
+elif defined(solaris):
+  type thread_t {.importc: "thread_t", header: "<thread.h>".} = distinct int
+  proc thr_self(): thread_t {.importc, header: "<thread.h>".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(thr_self())
+    result = threadId
+
+elif defined(haiku):
+  type thr_id {.importc: "thread_id", header: "<OS.h>".} = distinct int32
+  proc find_thread(name: cstring): thr_id {.importc, header: "<OS.h>".}
+
+  proc getThreadId*(): int =
+    ## Gets the ID of the currently running thread.
+    if threadId == 0:
+      threadId = int(find_thread(nil))
+    result = threadId
diff --git a/lib/system/threadlocalstorage.nim b/lib/system/threadlocalstorage.nim
index 30962ef77fcf..e772f270c59b 100644
--- a/lib/system/threadlocalstorage.nim
+++ b/lib/system/threadlocalstorage.nim
@@ -29,9 +29,6 @@ when defined(windows):
   proc terminateThread(hThread: SysThread, dwExitCode: int32): int32 {.
     stdcall, dynlib: "kernel32", importc: "TerminateThread".}
 
-  proc getCurrentThreadId(): int32 {.
-    stdcall, dynlib: "kernel32", importc: "GetCurrentThreadId".}
-
   type
     ThreadVarSlot = distinct int32
 
diff --git a/lib/system/threads.nim b/lib/system/threads.nim
index a9006b0c5c06..a8a413bcb5bc 100644
--- a/lib/system/threads.nim
+++ b/lib/system/threads.nim
@@ -343,94 +343,5 @@ else:
 proc createThread*(t: var Thread[void], tp: proc () {.thread, nimcall.}) =
   createThread[void](t, tp)
 
-# we need to cache current threadId to not perform syscall all the time
-var threadId {.threadvar.}: int
-
-when defined(windows):
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(getCurrentThreadId())
-    result = threadId
-
-elif defined(linux):
-  proc syscall(arg: clong): clong {.varargs, importc: "syscall", header: "<unistd.h>".}
-  when defined(amd64):
-    const NR_gettid = clong(186)
-  else:
-    var NR_gettid {.importc: "__NR_gettid", header: "<sys/syscall.h>".}: clong
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(syscall(NR_gettid))
-    result = threadId
-
-elif defined(dragonfly):
-  proc lwp_gettid(): int32 {.importc, header: "unistd.h".}
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(lwp_gettid())
-    result = threadId
-
-elif defined(openbsd):
-  proc getthrid(): int32 {.importc: "getthrid", header: "<unistd.h>".}
-
-  proc getThreadId*(): int =
-    ## get the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(getthrid())
-    result = threadId
-
-elif defined(netbsd):
-  proc lwp_self(): int32 {.importc: "_lwp_self", header: "<lwp.h>".}
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(lwp_self())
-    result = threadId
-
-elif defined(freebsd):
-  proc syscall(arg: cint, arg0: ptr cint): cint {.varargs, importc: "syscall", header: "<unistd.h>".}
-  var SYS_thr_self {.importc:"SYS_thr_self", header:"<sys/syscall.h>".}: cint
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    var tid = 0.cint
-    if threadId == 0:
-      discard syscall(SYS_thr_self, addr tid)
-      threadId = tid
-    result = threadId
-
-elif defined(macosx):
-  proc syscall(arg: cint): cint {.varargs, importc: "syscall", header: "<unistd.h>".}
-  var SYS_thread_selfid {.importc:"SYS_thread_selfid", header:"<sys/syscall.h>".}: cint
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(syscall(SYS_thread_selfid))
-    result = threadId
-
-elif defined(solaris):
-  type thread_t {.importc: "thread_t", header: "<thread.h>".} = distinct int
-  proc thr_self(): thread_t {.importc, header: "<thread.h>".}
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(thr_self())
-    result = threadId
-
-elif defined(haiku):
-  type thr_id {.importc: "thread_id", header: "<OS.h>".} = distinct int32
-  proc find_thread(name: cstring): thr_id {.importc, header: "<OS.h>".}
-
-  proc getThreadId*(): int =
-    ## Gets the ID of the currently running thread.
-    if threadId == 0:
-      threadId = int(find_thread(nil))
-    result = threadId
+when not defined(gcOrc):
+  include threadids