diff --git a/Project.toml b/Project.toml
index b54e8b122..225897708 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "Mooncake"
 uuid = "da2b9cff-9c12-43a0-ae48-6db2b0edb7d6"
 authors = ["Will Tebbutt, Hong Ge, and contributors"]
-version = "0.4.20"
+version = "0.4.21"
 
 [deps]
 ADTypes = "47edcb42-4c32-4615-8424-f2b9edc5f35b"
diff --git a/src/rrules/builtins.jl b/src/rrules/builtins.jl
index 3e4a101f7..4e0ed19a1 100644
--- a/src/rrules/builtins.jl
+++ b/src/rrules/builtins.jl
@@ -789,7 +789,7 @@ function generate_hand_written_rrule!!_test_cases(rng_ctor, ::Val{:builtins})
         # Core._primitivetype -- NEEDS IMPLEMENTING AND TESTING
         # Core._setsuper! -- NEEDS IMPLEMENTING AND TESTING
         # Core._structtype -- NEEDS IMPLEMENTING AND TESTING
-        (false, :none, nothing, Core._svec_ref, svec(5, 4), 2),
+        (false, :none, _range, Core._svec_ref, svec(5, 4), 2),
         # Core._typebody! -- NEEDS IMPLEMENTING AND TESTING
         (false, :stability, nothing, <:, Float64, Int),
         (false, :stability, nothing, <:, Any, Float64),
@@ -799,8 +799,8 @@ function generate_hand_written_rrule!!_test_cases(rng_ctor, ::Val{:builtins})
         (false, :stability, nothing, ===, randn(5), randn(3)),
         (false, :stability, nothing, ===, 5.0, 5.0),
         (true, :stability, nothing, Core._typevar, :T, Union{}, Any),
-        (false, :none, (lb=1e-3, ub=100.0), Core.apply_type, Vector, Float64),
-        (false, :none, (lb=1e-3, ub=100.0), Core.apply_type, Array, Float64, 2),
+        (false, :none, _range, Core.apply_type, Vector, Float64),
+        (false, :none, _range, Core.apply_type, Array, Float64, 2),
         # Core.compilerbarrier -- NEEDS IMPLEMENTING AND TESTING
         # Core.const_arrayref -- NEEDS IMPLEMENTING AND TESTING
         # Core.donotdelete -- NEEDS IMPLEMENTING AND TESTING
diff --git a/src/test_resources.jl b/src/test_resources.jl
index b76222b26..b6f821338 100644
--- a/src/test_resources.jl
+++ b/src/test_resources.jl
@@ -562,6 +562,10 @@ function non_const_global_ref(y::Float64)
     return __x_for_non_const_global_ref
 end
 
+# The inferred type of `TypeVar(...)` is `CC.PartialTypeVar`. Thanks to Jameson Nash for
+# pointing out this pleasantly simple test case.
+partial_type_var() = TypeVar(:a, Union{}, Any)
+
 function generate_test_functions()
     return Any[
         (false, :allocs, nothing, const_tester),
@@ -738,6 +742,7 @@ function generate_test_functions()
         (false, :allocs, nothing, inlinable_invoke_call, 5.0),
         (false, :none, nothing, inlinable_vararg_invoke_call, (2, 2), 5.0, 4.0, 3.0, 2.0),
         (false, :none, nothing, hvcat, (2, 2), 3.0, 2.0, 0.0, 1.0),
+        (false, :none, nothing, partial_type_var),
     ]
 end