3 files changed, 27 insertions, 2 deletions
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index f08c17904584..0fadb738d529 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -125,8 +125,10 @@ fn pure_builtins() -> Vec<Builtin> {
                 Ok(Value::String(format!("{}", value).into()))
             })
         }),
-        Builtin::new("typeOf", 1, |args, _| {
-            Ok(Value::String(args[0].type_of().into()))
+        Builtin::new("typeOf", 1, |args, vm| {
+            force!(vm, &args[0], value, {
+                Ok(Value::String(value.type_of().into()))
+            })
         }),
     ]
 }
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.exp b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.exp
new file mode 100644
index 000000000000..0e22da8d56ee
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.exp
@@ -0,0 +1 @@
+[ "null" "bool" "bool" "int" "int" "float" "string" "string" "set" "set" "set" "list" "lambda" "path" ]
diff --git a/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.nix b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.nix
new file mode 100644
index 000000000000..38d7ffee6169
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/eval-okay-builtins-type-of.nix
@@ -0,0 +1,22 @@
+let
+  fix = f: let x = f x; in x;
+in
+
+fix (self:
+  [
+    (builtins.typeOf null)
+    (builtins.typeOf true)
+    (builtins.typeOf (true && false))
+    (builtins.typeOf 12)
+    (builtins.typeOf (builtins.add 21 21))
+    (builtins.typeOf 1.2)
+    (builtins.typeOf "foo")
+    (builtins.typeOf "${"foo" + "bar"}baz")
+    (builtins.typeOf {})
+    (builtins.typeOf { foo.bar = 32; }.foo)
+    (builtins.typeOf ({ name = "foo"; value = 13; } // { name = "bar"; }))
+    (builtins.typeOf self)
+    (builtins.typeOf fix)
+    (builtins.typeOf /nix/store)
+  ]
+)