diff --git a/Project.toml b/Project.toml
index 23cdbd91..e0bdc1b9 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,7 +3,7 @@ uuid = "6f1fad26-d15e-5dc8-ae53-837a1d7b8c9f"
 license = "MIT"
 desc = "Tape based task copying in Turing"
 repo = "https://github.com/TuringLang/Libtask.jl.git"
-version = "0.6.6"
+version = "0.6.7"
 
 [deps]
 IRTools = "7869d1d1-7146-5819-86e3-90919afe41df"
diff --git a/src/tapedfunction.jl b/src/tapedfunction.jl
index 7f7c8c8b..3ff032ca 100644
--- a/src/tapedfunction.jl
+++ b/src/tapedfunction.jl
@@ -291,6 +291,9 @@ deeply copied, one can add a method to this function.
 """
 function tape_copy end
 tape_copy(x) = x
+# Core.Box is used as closure captured variable container, so we should tape_copy its contents
+tape_copy(x::Core.Box) = Core.Box(tape_copy(x.contents))
+# ?? should we deepcopy Array and Dict by default?
 # tape_copy(x::Array) = deepcopy(x)
 # tape_copy(x::Dict) = deepcopy(x)