diff --git a/test/rulesets/Base/mapreduce.jl b/test/rulesets/Base/mapreduce.jl
index 8a08a37b4..5aeefecb0 100644
--- a/test/rulesets/Base/mapreduce.jl
+++ b/test/rulesets/Base/mapreduce.jl
@@ -108,8 +108,12 @@ const CFG = ChainRulesTestUtils.ADviaRuleConfig()
         test_rrule(sum, sqrt, randn(5) .> 0) 
         test_rrule(sum, sqrt, randn(5,5) .> 0; fkwargs=(;dims=1))
         # ... and Bool produced by function
+        # https://github.com/JuliaDiff/ChainRulesTestUtils.jl/issues/219
         @test_skip test_rrule(sum, iszero, randn(5))  # DimensionMismatch("second dimension of A, 1, does not match length of x, 0")
 
+        _, pb = rrule(CFG, sum, iszero, randn(5))
+        @test pb(1.0) == (NoTangent(), NoTangent(), NoTangent(),)
+
         # Functions that return a Vector
         # see https://github.com/FluxML/Zygote.jl/issues/1074
         test_rrule(sum, make_two_vec, [1.0, 3.0, 5.0, 7.0])