diff --git a/lix/legacy/nix-instantiate.cc b/lix/legacy/nix-instantiate.cc
index 74db1c76b..7ba3e0d51 100644
--- a/lix/legacy/nix-instantiate.cc
+++ b/lix/legacy/nix-instantiate.cc
@@ -51,7 +51,7 @@ void processExpr(EvalState & state, const Strings & attrPaths,
             if (output == okXML)
                 printValueAsXML(state, strict, location, vRes, std::cout, context, noPos);
             else if (output == okJSON) {
-                printValueAsJSON(state, strict, vRes, v.determinePos(noPos), std::cout, context);
+                printValueAsJSON(state, strict, vRes, noPos, std::cout, context);
                 std::cout << std::endl;
             } else {
                 if (strict) state.forceValueDeep(vRes);
diff --git a/lix/libexpr/value-to-json.cc b/lix/libexpr/value-to-json.cc
index 27b6aecb6..60efd13bb 100644
--- a/lix/libexpr/value-to-json.cc
+++ b/lix/libexpr/value-to-json.cc
@@ -102,7 +102,7 @@ JSON printValueAsJSON(EvalState & state, bool strict,
                 "cannot convert %1% to JSON",
                 showType(v)
             )
-            .atPos(v.determinePos(pos))
+            .atPos(pos)
             .debugThrow();
     }
     return out;
diff --git a/tests/functional/lang/eval-fail-toJSON-nested.err.exp b/tests/functional/lang/eval-fail-toJSON-nested.err.exp
new file mode 100644
index 000000000..1dbbdcd81
--- /dev/null
+++ b/tests/functional/lang/eval-fail-toJSON-nested.err.exp
@@ -0,0 +1,18 @@
+error:
+       … while calling the 'toJSON' builtin
+         at /pwd/lang/eval-fail-toJSON-nested.nix:1:1:
+            1| builtins.toJSON { foo = a: 1; }
+             | ^
+            2|
+
+       … while evaluating attribute 'foo'
+         at /pwd/lang/eval-fail-toJSON-nested.nix:1:19:
+            1| builtins.toJSON { foo = a: 1; }
+             |                   ^
+            2|
+
+       error: cannot convert a function to JSON
+       at /pwd/lang/eval-fail-toJSON-nested.nix:1:19:
+            1| builtins.toJSON { foo = a: 1; }
+             |                   ^
+            2|
diff --git a/tests/functional/lang/eval-fail-toJSON-nested.nix b/tests/functional/lang/eval-fail-toJSON-nested.nix
new file mode 100644
index 000000000..46cab20cb
--- /dev/null
+++ b/tests/functional/lang/eval-fail-toJSON-nested.nix
@@ -0,0 +1 @@
+builtins.toJSON { foo = a: 1; }