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diff --git a/testsuite/tests/typecheck/should_fail/tcfail080.hs b/testsuite/tests/typecheck/should_fail/tcfail080.hs
new file mode 100644
index 0000000000..b2a62cea54
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+++ b/testsuite/tests/typecheck/should_fail/tcfail080.hs
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+{-# LANGUAGE MultiParamTypeClasses #-}
+
+-- !!! Multi-param type classes test: ambiguity bug
+
+-- GHC actually accepts this program because
+--	q :: Collection c a => a -> Bool
+-- and there is no a priori reason to suppose that
+-- q would be ambiguous in every context. For example,
+-- it could be fine if we had
+--	instance c Int where ...
+-- Of course, it'd be hard to fill in the "..." in this particular
+-- case, but that relies on observations about the form of the types
+-- of the class methods, surely beyond what a compiler should do.
+-- That's why GHC accepts it
+
+module ShouldFail where
+
+class Collection c a where
+    empty :: c a
+    add :: a -> c a -> c a
+    isempty :: c a -> Bool
+
+singleton x = add x empty
+
+q x = isempty (singleton x)
+
+