3 files changed, 20 insertions, 0 deletions
diff --git a/testsuite/tests/indexed-types/should_fail/T12041.hs b/testsuite/tests/indexed-types/should_fail/T12041.hs
new file mode 100644
index 0000000000..9210280920
--- /dev/null
+++ b/testsuite/tests/indexed-types/should_fail/T12041.hs
@@ -0,0 +1,12 @@
+{-# Language PolyKinds, TypeFamilies #-}
+
+module T12041 where
+
+import Data.Kind
+
+class Category (p :: i -> i -> Type) where
+  type Ob p :: i -> Constraint
+
+data I a b
+instance Category I where
+  type Ob I = (~) Int
diff --git a/testsuite/tests/indexed-types/should_fail/T12041.stderr b/testsuite/tests/indexed-types/should_fail/T12041.stderr
new file mode 100644
index 0000000000..006ca37bae
--- /dev/null
+++ b/testsuite/tests/indexed-types/should_fail/T12041.stderr
@@ -0,0 +1,7 @@
+
+T12041.hs:12:15: error:
+    • Expected kind ‘i -> Constraint’,
+        but ‘(~) Int’ has kind ‘* -> Constraint’
+    • In the type ‘(~) Int’
+      In the type instance declaration for ‘Ob’
+      In the instance declaration for ‘Category I’
diff --git a/testsuite/tests/indexed-types/should_fail/all.T b/testsuite/tests/indexed-types/should_fail/all.T
index dfc0326154..041282eadf 100644
--- a/testsuite/tests/indexed-types/should_fail/all.T
+++ b/testsuite/tests/indexed-types/should_fail/all.T
@@ -140,3 +140,4 @@ test('T10899', normal, compile_fail, [''])
 test('T11136', normal, compile_fail, [''])
 test('T7788', normal, compile_fail, [''])
 test('T11450', normal, compile_fail, [''])
+test('T12041', normal, compile_fail, [''])