diff --git a/tests/functional2/lang/fromJSON-overflowing/eval-fail.err.exp b/tests/functional2/lang/fromJSON-overflowing/eval-fail-overflow.err.exp
similarity index 100%
rename from tests/functional2/lang/fromJSON-overflowing/eval-fail.err.exp
rename to tests/functional2/lang/fromJSON-overflowing/eval-fail-overflow.err.exp
diff --git a/tests/functional2/lang/fromJSON-overflowing/eval-okay-underflow.out.exp b/tests/functional2/lang/fromJSON-overflowing/eval-okay-underflow.out.exp
new file mode 100644
index 000000000..1f835a11b
--- /dev/null
+++ b/tests/functional2/lang/fromJSON-overflowing/eval-okay-underflow.out.exp
@@ -0,0 +1 @@
+{ attr = -9.22337e+18; }
diff --git a/tests/functional2/lang/fromJSON-overflowing/in.nix b/tests/functional2/lang/fromJSON-overflowing/in-overflow.nix
similarity index 100%
rename from tests/functional2/lang/fromJSON-overflowing/in.nix
rename to tests/functional2/lang/fromJSON-overflowing/in-overflow.nix
diff --git a/tests/functional2/lang/fromJSON-overflowing/in-underflow.nix b/tests/functional2/lang/fromJSON-overflowing/in-underflow.nix
new file mode 100644
index 000000000..005403f98
--- /dev/null
+++ b/tests/functional2/lang/fromJSON-overflowing/in-underflow.nix
@@ -0,0 +1 @@
+builtins.fromJSON ''{"attr": -9223372036854775809}''