diff --git a/src/HordeAd/Core/Ast.hs b/src/HordeAd/Core/Ast.hs
index 7b73240b2..38a3708cb 100644
--- a/src/HordeAd/Core/Ast.hs
+++ b/src/HordeAd/Core/Ast.hs
@@ -790,7 +790,7 @@ instance Boolean AstBool where
   b ||* c = AstB2 OrOp b c
 
 
--- * Boolean definitions and instances
+-- * Boolean definitions
 
 class Boolean (BoolOf f) => IfF (f :: TensorType ty) where
   ifF :: (GoodScalar r, HasSingletonDict y)
diff --git a/test/simplified/TestAdaptorSimplified.hs b/test/simplified/TestAdaptorSimplified.hs
index 49f4e080a..b352ae64f 100644
--- a/test/simplified/TestAdaptorSimplified.hs
+++ b/test/simplified/TestAdaptorSimplified.hs
@@ -166,6 +166,7 @@ testTrees =
   , testCase "2emptyArgs0" testEmptyArgs0
   , testCase "2emptyArgs1" testEmptyArgs1
   , testCase "2emptyArgs4" testEmptyArgs4
+  , testCase "2filterPositiveFail" testFilterPositiveFail
   , testCase "2blowupPP" fblowupPP
   , testCase "2blowupLetPP" fblowupLetPP
   , blowupTests
@@ -1884,6 +1885,25 @@ testEmptyArgs4 =
           (\t -> rbuild [2, 5, 11, 0] (const $ emptyArgs t))
           (Flip $ OR.fromList [1] [0.24]))
 
+filterPositiveFail :: ADReady ranked
+                   => ranked Double 1 -> ranked Double 1
+filterPositiveFail v =
+  let l = runravelToList v
+      -- l2 = filter (\x -> x >= 0) l
+      -- Could not deduce ‘Ord (ranked Double 0)’
+      -- l2 = filter (\x -> x >=. 0) l
+      -- Could not deduce ‘BoolOf ranked ~ Bool’
+      l2 = take 3 l  -- the most I can do
+  in rfromList l2
+
+testFilterPositiveFail :: Assertion
+testFilterPositiveFail =
+  assertEqualUpToEpsilon' 1e-10
+    (OR.fromList [5] [1.0,1.0,1.0,0.0,0.0])
+    (rev' @Double @1
+          filterPositiveFail
+          (Flip $ OR.fromList [5] [0.24, 52, -0.5, 0.33, 0.1]))
+
 -- Catastrophic loss of sharing prevented.
 fblowup :: forall ranked r. (ADReady ranked, GoodScalar r, Differentiable r)
         => Int -> ranked r 1 -> ranked r 0