fixes #6234

tests/ccgbugs/twrongrefcounting.nim

@@ -0,0 +1,22 @@
+discard """
+  output: '''ok'''
+  cmd: "nim c -r --gc:refc -d:useGcAssert -d:useSysAssert -d:fulldebug -d:smokeCycles $file"
+"""
+# bug #6234
+type
+    Foo = ref object
+        s: seq[Bar]
+    Bar = ref object
+        f: Foo
+
+proc test() =
+    var f = Foo.new()
+    for i in 0 .. 5:
+        f.s = @[]
+        for j in 0 .. 5:
+            var b = Bar.new()
+            b.f = f
+            f.s.add(b)
+
+test()
+echo "ok"