diff --git a/tests/lang/eval-okay-groupBy.exp b/tests/lang/eval-okay-groupBy.exp
new file mode 100644
index 000000000..bfca5652a
--- /dev/null
+++ b/tests/lang/eval-okay-groupBy.exp
@@ -0,0 +1 @@
+{ "1" = [ 9 ]; "2" = [ 8 ]; "3" = [ 13 29 ]; "4" = [ 3 4 10 11 17 18 ]; "5" = [ 0 23 26 28 ]; "6" = [ 1 12 21 27 30 ]; "7" = [ 7 22 ]; "8" = [ 14 ]; "9" = [ 19 ]; b = [ 16 25 ]; c = [ 24 ]; d = [ 2 ]; e = [ 5 6 15 31 ]; f = [ 20 ]; }
diff --git a/tests/lang/eval-okay-groupBy.nix b/tests/lang/eval-okay-groupBy.nix
new file mode 100644
index 000000000..862d89dbd
--- /dev/null
+++ b/tests/lang/eval-okay-groupBy.nix
@@ -0,0 +1,5 @@
+with import ./lib.nix;
+
+builtins.groupBy (n:
+  builtins.substring 0 1 (builtins.hashString "sha256" (toString n))
+) (range 0 31)