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diff --git a/testsuite/tests/typecheck/should_compile/T4418.hs b/testsuite/tests/typecheck/should_compile/T4418.hs
new file mode 100644
index 0000000000..9b90fd61a6
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T4418.hs
@@ -0,0 +1,20 @@
+{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
+
+module Ambiguity where
+
+class C1 a b | b -> a
+class (C1 a b) => C2 a b where
+  foo :: b -> b
+
+data A = A
+data B = B
+instance C1 A B 
+instance C2 A B where foo = error "urk"
+
+-- this is accepted by both 6.12.3 and 7  
+runFoo1 :: C2 a b => b -> b  
+runFoo1 = foo
+
+-- this is accepted by 6.12.3, but not by 7
+runFoo2 :: B -> B
+runFoo2 = foo