diff --git a/tests/functional2/lang/builtins.fromJSON/eval-okay-duplicate-keys.out.exp b/tests/functional2/lang/builtins.fromJSON/eval-okay-duplicate-keys.out.exp
new file mode 100644
index 000000000..bba5bcfa8
--- /dev/null
+++ b/tests/functional2/lang/builtins.fromJSON/eval-okay-duplicate-keys.out.exp
@@ -0,0 +1 @@
+{ key = "three"; }
diff --git a/tests/functional2/lang/builtins.fromJSON/in-duplicate-keys.nix b/tests/functional2/lang/builtins.fromJSON/in-duplicate-keys.nix
new file mode 100644
index 000000000..009fc868d
--- /dev/null
+++ b/tests/functional2/lang/builtins.fromJSON/in-duplicate-keys.nix
@@ -0,0 +1,8 @@
+# Duplicate JSON keys should always drop all but the latest value
+builtins.fromJSON ''
+  {
+    "key": "one",
+    "key": "two",
+    "key": "three"
+  }
+''