diff --git a/compiler/types.nim b/compiler/types.nim
index 2c2dec639c9a2..d2517127a9fda 100644
--- a/compiler/types.nim
+++ b/compiler/types.nim
@@ -396,9 +396,9 @@ proc canFormAcycleAux(marker: var IntSet, typ: PType, startId: int): bool =
       result = true
     elif not containsOrIncl(marker, t.id):
       for i in 0..<t.len:
-        result = canFormAcycleAux(marker, t[i], abs startId)
+        result = canFormAcycleAux(marker, t[i], startId)
         if result: return
-      if t.n != nil: result = canFormAcycleNode(marker, t.n, abs startId)
+      if t.n != nil: result = canFormAcycleNode(marker, t.n, startId)
     # Inheritance can introduce cyclic types, however this is not relevant
     # as the type that is passed to 'new' is statically known!
     # er but we use it also for the write barrier ...
@@ -415,10 +415,7 @@ proc isFinal*(t: PType): bool =
 proc canFormAcycle*(typ: PType): bool =
   var marker = initIntSet()
   let t = skipTypes(typ, abstractInst+{tyOwned}-{tyTypeDesc})
-  # startId begins with a negative value that is only in the first recursion
-  # and the following recursions set to its real value. This fixes
-  # bug #21753:
-  result = canFormAcycleAux(marker, t, -t.id)
+  result = canFormAcycleAux(marker, t, t.id)
 
 proc mutateTypeAux(marker: var IntSet, t: PType, iter: TTypeMutator,
                    closure: RootRef): PType
diff --git a/lib/system/cellseqs_v1.nim b/lib/system/cellseqs_v1.nim
index 1952491b37778..1a305aa428d62 100644
--- a/lib/system/cellseqs_v1.nim
+++ b/lib/system/cellseqs_v1.nim
@@ -16,18 +16,21 @@ type
     d: PCellArray
 
 proc contains(s: CellSeq, c: PCell): bool {.inline.} =
-  for i in 0 .. s.len-1:
-    if s.d[i] == c: return true
+  for i in 0 ..< s.len:
+    if s.d[i] == c:
+      return true
   return false
 
+proc resize(s: var CellSeq) =
+  s.cap = s.cap * 3 div 2
+  let d = cast[PCellArray](alloc(s.cap * sizeof(PCell)))
+  copyMem(d, s.d, s.len * sizeof(PCell))
+  dealloc(s.d)
+  s.d = d
+
 proc add(s: var CellSeq, c: PCell) {.inline.} =
   if s.len >= s.cap:
-    s.cap = s.cap * 3 div 2
-    var d = cast[PCellArray](alloc(s.cap * sizeof(PCell)))
-    copyMem(d, s.d, s.len * sizeof(PCell))
-    dealloc(s.d)
-    s.d = d
-    # XXX: realloc?
+    resize(s)
   s.d[s.len] = c
   inc(s.len)
 
diff --git a/lib/system/orc.nim b/lib/system/orc.nim
index 2addefdcfedee..a56a0c057427e 100644
--- a/lib/system/orc.nim
+++ b/lib/system/orc.nim
@@ -350,7 +350,7 @@ const
 when defined(nimStressOrc):
   const rootsThreshold = 10 # broken with -d:nimStressOrc: 10 and for havlak iterations 1..8
 else:
-  var rootsThreshold {.threadvar.}: int
+  var rootsThreshold = defaultThreshold
 
 proc partialCollect(lowMark: int) =
   when false:
@@ -392,13 +392,13 @@ proc collectCycles() =
     # of the cycle collector's effectiveness:
     # we're effective when we collected 50% or more of the nodes
     # we touched. If we're effective, we can reset the threshold:
-    if j.keepThreshold and rootsThreshold <= 0:
+    if j.keepThreshold and rootsThreshold <= defaultThreshold:
       discard
     elif j.freed * 2 >= j.touched:
       when not defined(nimFixedOrc):
         rootsThreshold = max(rootsThreshold div 3 * 2, 16)
       else:
-        rootsThreshold = 0
+        rootsThreshold = defaultThreshold
       #cfprintf(cstderr, "[collectCycles] freed %ld, touched %ld new threshold %ld\n", j.freed, j.touched, rootsThreshold)
     elif rootsThreshold < high(int) div 4:
       rootsThreshold = rootsThreshold * 3 div 2
@@ -411,7 +411,7 @@ proc registerCycle(s: Cell; desc: PNimTypeV2) =
   if roots.d == nil: init(roots)
   add(roots, s, desc)
 
-  if roots.len >= rootsThreshold+defaultThreshold:
+  if roots.len >= rootsThreshold:
     collectCycles()
   when logOrc:
     writeCell("[added root]", s, desc)
@@ -427,7 +427,7 @@ proc GC_enableOrc*() =
   ## Enables the cycle collector subsystem of `--gc:orc`. This is a `--gc:orc`
   ## specific API. Check with `when defined(gcOrc)` for its existence.
   when not defined(nimStressOrc):
-    rootsThreshold = 0
+    rootsThreshold = defaultThreshold
 
 proc GC_disableOrc*() =
   ## Disables the cycle collector subsystem of `--gc:orc`. This is a `--gc:orc`
diff --git a/tests/arc/tasyncleak.nim b/tests/arc/tasyncleak.nim
index 8e3a7b3e7b298..eb0c4521311bc 100644
--- a/tests/arc/tasyncleak.nim
+++ b/tests/arc/tasyncleak.nim
@@ -1,5 +1,5 @@
 discard """
-  outputsub: "(allocCount: 4050, deallocCount: 4048)"
+  outputsub: "(allocCount: 4302, deallocCount: 4300)"
   cmd: "nim c --gc:orc -d:nimAllocStats $file"
 """
 
diff --git a/tests/arc/topt_no_cursor.nim b/tests/arc/topt_no_cursor.nim
index 32652b60a55b5..ddcc549d1fcbf 100644
--- a/tests/arc/topt_no_cursor.nim
+++ b/tests/arc/topt_no_cursor.nim
@@ -1,6 +1,6 @@
 discard """
   nimoutFull: true
-  cmd: '''nim c -r --warnings:off --hints:off --mm:arc --expandArc:newTarget --expandArc:delete --expandArc:p1 --expandArc:tt --hint:Performance:off --assertions:off --expandArc:extractConfig --expandArc:mergeShadowScope --expandArc:check $file'''
+  cmd: '''nim c -r --warnings:off --hints:off --gc:arc --expandArc:newTarget --expandArc:delete --expandArc:p1 --expandArc:tt --hint:Performance:off --assertions:off --expandArc:extractConfig --expandArc:mergeShadowScope --expandArc:check $file'''
   nimout: '''
 --expandArc: newTarget