diff --git a/testsuite/tests/typecheck/should_fail/T5957.hs b/testsuite/tests/typecheck/should_fail/T5957.hs
new file mode 100644
index 0000000000000000000000000000000000000000..c168a00f3a357b2207db3e3aaa8d2d6139b6cf04
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T5957.hs
@@ -0,0 +1,4 @@
+module T5957 where
+
+flex :: Int -> Show a => a -> String
+flex i a = show a ++ show i
diff --git a/testsuite/tests/typecheck/should_fail/T5957.stderr b/testsuite/tests/typecheck/should_fail/T5957.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..c0bc12a7a2b419197c8939524fac86af2db81dae
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T5957.stderr
@@ -0,0 +1,6 @@
+
+T5957.hs:3:9:
+    Illegal polymorphic or qualified type: Show a => a -> String
+    Perhaps you intended to use -XRankNTypes or -XRank2Types
+    In the type signature for `flex':
+      flex :: Int -> Show a => a -> String
diff --git a/testsuite/tests/typecheck/should_fail/all.T b/testsuite/tests/typecheck/should_fail/all.T
index 9d4d6a03c4654e990095e7a1e23f04dfadd71e73..caf92fb01149b1b05c5f6956ee3a39b14f08b242 100644
--- a/testsuite/tests/typecheck/should_fail/all.T
+++ b/testsuite/tests/typecheck/should_fail/all.T
@@ -271,3 +271,4 @@ test('T5573b', normal, compile_fail, [''])
 test('T5689', normal, compile_fail, [''])
 test('T5684', normal, compile_fail, [''])
 test('T5858', normal, compile_fail, [''])
+test('T5957', normal, compile_fail, [''])