3 files changed, 15 insertions, 0 deletions
diff --git a/testsuite/tests/showIface/T17871.hs b/testsuite/tests/showIface/T17871.hs
new file mode 100644
index 0000000000..bc2b0c791a
--- /dev/null
+++ b/testsuite/tests/showIface/T17871.hs
@@ -0,0 +1,5 @@
+module T17871 where
+
+import T17871a
+
+instance C ()
diff --git a/testsuite/tests/showIface/T17871a.hs b/testsuite/tests/showIface/T17871a.hs
new file mode 100644
index 0000000000..151e994690
--- /dev/null
+++ b/testsuite/tests/showIface/T17871a.hs
@@ -0,0 +1,9 @@
+-- A.hs
+module T17871a (C(..)) where
+
+class C a where
+  m :: a -> a
+  m = identity
+
+identity :: a -> a
+identity x = x
diff --git a/testsuite/tests/showIface/all.T b/testsuite/tests/showIface/all.T
index 34550f696b..e2ec264431 100644
--- a/testsuite/tests/showIface/all.T
+++ b/testsuite/tests/showIface/all.T
@@ -5,3 +5,4 @@ test('DocsInHiFile0',
 test('DocsInHiFile1',
      extra_files(['DocsInHiFile.hs']),
      makefile_test, ['DocsInHiFile1'])
+test('T17871', [extra_files(['T17871a.hs'])], multimod_compile, ['T17871', '-v0'])