diff --git a/compiler/injectdestructors.nim b/compiler/injectdestructors.nim
index 40a4b74213..146309bbe5 100644
--- a/compiler/injectdestructors.nim
+++ b/compiler/injectdestructors.nim
@@ -636,7 +636,8 @@ proc reverseDestroys(destroys: seq[PNode]): seq[PNode] =
     result.add destroys[i]
 
 proc injectDestructorCalls*(g: ModuleGraph; owner: PSym; n: PNode): PNode =
-  if sfGeneratedOp in owner.flags or (owner.kind == skIterator and isInlineIterator(owner.typ)): return n
+  if sfGeneratedOp in owner.flags or (owner.kind == skIterator and isInlineIterator(owner.typ)):
+    return n
   var c: Con
   c.owner = owner
   c.destroys = newNodeI(nkStmtList, n.info)
diff --git a/compiler/lambdalifting.nim b/compiler/lambdalifting.nim
index 2ea5f5263a..34b9d7ecc3 100644
--- a/compiler/lambdalifting.nim
+++ b/compiler/lambdalifting.nim
@@ -245,7 +245,7 @@ proc liftIterSym*(g: ModuleGraph; n: PNode; owner: PSym): PNode =
   var env: PNode
   if owner.isIterator:
     let it = getHiddenParam(g, owner)
-    addUniqueField(it.typ.sons[0], hp, g.cache)
+    addUniqueField(it.typ.skipTypes({tyOwned}).sons[0], hp, g.cache)
     env = indirectAccess(newSymNode(it), hp, hp.info)
   else:
     let e = newSym(skLet, iter.name, owner, n.info)
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 518b5e5e8b..ace2c79667 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -670,7 +670,7 @@ proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
   result = n
   var length = len(n)
   let iterBase = n.sons[length-2].typ
-  var iter = skipTypes(iterBase, {tyGenericInst, tyAlias, tySink})
+  var iter = skipTypes(iterBase, {tyGenericInst, tyAlias, tySink, tyOwned})
   var iterAfterVarLent = iter.skipTypes({tyLent, tyVar})
   # length == 3 means that there is one for loop variable
   # and thus no tuple unpacking:
@@ -683,18 +683,18 @@ proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
           var v = symForVar(c, n[0][i])
           if getCurrOwner(c).kind == skModule: incl(v.flags, sfGlobal)
           case iter.kind
-            of tyVar:
-              v.typ = newTypeS(tyVar, c)
-              v.typ.sons.add iterAfterVarLent[i]
-              if tfVarIsPtr in iter.flags:
-                v.typ.flags.incl tfVarIsPtr
-            of tyLent:
-              v.typ = newTypeS(tyLent, c)
-              v.typ.sons.add iterAfterVarLent[i]
-              if tfVarIsPtr in iter.flags:
-                v.typ.flags.incl tfVarIsPtr
-            else:
-              v.typ = iter.sons[i]
+          of tyVar:
+            v.typ = newTypeS(tyVar, c)
+            v.typ.sons.add iterAfterVarLent[i]
+            if tfVarIsPtr in iter.flags:
+              v.typ.flags.incl tfVarIsPtr
+          of tyLent:
+            v.typ = newTypeS(tyLent, c)
+            v.typ.sons.add iterAfterVarLent[i]
+            if tfVarIsPtr in iter.flags:
+              v.typ.flags.incl tfVarIsPtr
+          else:
+            v.typ = iter.sons[i]
           n.sons[0][i] = newSymNode(v)
           if sfGenSym notin v.flags: addDecl(c, v)
           elif v.owner == nil: v.owner = getCurrOwner(c)
@@ -717,14 +717,14 @@ proc semForVars(c: PContext, n: PNode; flags: TExprFlags): PNode =
       if n.sons[i].kind == nkVarTuple:
         var mutable = false
         var isLent = false
-        iter[i] = case iter[i].kind
-          of tyVar:
-            mutable = true
-            iter[i].skipTypes({tyVar})
-          of tyLent:
-            isLent = true
-            iter[i].skipTypes({tyLent})
-          else: iter[i]
+        case iter[i].kind
+        of tyVar:
+          mutable = true
+          iter[i] = iter[i].skipTypes({tyVar})
+        of tyLent:
+          isLent = true
+          iter[i] = iter[i].skipTypes({tyLent})
+        else: discard
 
         if len(n[i])-1 != len(iter[i]):
           localError(c.config, n[i].info, errWrongNumberOfVariables)
@@ -871,8 +871,7 @@ proc semFor(c: PContext, n: PNode; flags: TExprFlags): PNode =
       result.kind = nkParForStmt
     else:
       result = semForFields(c, n, call.sons[0].sym.magic)
-  elif isCallExpr and call.sons[0].typ.callConv == ccClosure and
-      tfIterator in call.sons[0].typ.flags:
+  elif isCallExpr and isClosureIterator(call.sons[0].typ.skipTypes(abstractInst)):
     # first class iterator:
     result = semForVars(c, n, flags)
   elif not isCallExpr or call.sons[0].kind != nkSym or
@@ -1984,6 +1983,9 @@ proc semIterator(c: PContext, n: PNode): PNode =
     s.typ.callConv = ccInline
   if n.sons[bodyPos].kind == nkEmpty and s.magic == mNone:
     localError(c.config, n.info, errImplOfXexpected % s.name.s)
+  if optOwnedRefs in c.config.globalOptions and result.typ != nil:
+    result.typ = makeVarType(c, result.typ, tyOwned)
+    result.typ.callConv = ccClosure
 
 proc semProc(c: PContext, n: PNode): PNode =
   result = semProcAux(c, n, skProc, procPragmas)
diff --git a/compiler/transf.nim b/compiler/transf.nim
index b95733a37e..5660bcd8c9 100644
--- a/compiler/transf.nim
+++ b/compiler/transf.nim
@@ -608,7 +608,7 @@ proc transformFor(c: PTransf, n: PNode): PTransNode =
     return result
   c.breakSyms.add(labl)
   if call.kind notin nkCallKinds or call.sons[0].kind != nkSym or
-      call.sons[0].typ.callConv == ccClosure:
+      call.sons[0].typ.skipTypes(abstractInst).callConv == ccClosure:
     result[1] = n.PTransNode
     result[1][^1] = transformLoopBody(c, n[^1])
     result[1][^2] = transform(c, n[^2])
diff --git a/tests/destructor/tsimpleclosure.nim b/tests/destructor/tsimpleclosure.nim
index 43b5cb2b63..583cc7d880 100644
--- a/tests/destructor/tsimpleclosure.nim
+++ b/tests/destructor/tsimpleclosure.nim
@@ -44,5 +44,21 @@ ok0()
 var ok1 = say
 ok1()
 
+when false:
+  # bug #12443
+  func newStringIterator(s: string): owned(iterator(): char) =
+    result = iterator(): char =
+      var pos = 0
+      while pos < s.len:
+        yield s[pos]
+        inc pos
+
+  proc stringIter() =
+    let si = newStringIterator("foo")
+    for i in si():
+      echo i
+
+  stringIter()
+
 let (a, d) = allocCounters()
 discard cprintf("%ld %ld  alloc/dealloc pairs: %ld\n", a, d, system.allocs)