diff --git a/test/threads.jl b/test/threads.jl
index 24da56e2b89fd..7b4558091022b 100644
--- a/test/threads.jl
+++ b/test/threads.jl
@@ -357,12 +357,12 @@ end
 
 @testset "jl_*affinity" begin
     cpumasksize = @ccall uv_cpumask_size()::Cint
-    if !Sys.iswindows() && cpumasksize > 0 # otherwise affinities are not supported on the platform (UV_ENOTSUP)
-        mask = zeros(Cchar, cpumasksize);
+    if cpumasksize > 0 # otherwise affinities are not supported on the platform (UV_ENOTSUP)
         jl_getaffinity = (tid, mask, cpumasksize) -> ccall(:jl_getaffinity, Int32, (Int16, Ptr{Cchar}, Int32), tid, mask, cpumasksize)
         jl_setaffinity = (tid, mask, cpumasksize) -> ccall(:jl_setaffinity, Int32, (Int16, Ptr{Cchar}, Int32), tid, mask, cpumasksize)
-        @test jl_getaffinity(1, mask, cpumasksize) == 0
-        fill!(mask, 1)
-        @test jl_setaffinity(1, mask, cpumasksize) == 0
+        mask = zeros(Cchar, cpumasksize)
+        @test jl_getaffinity(0, mask, cpumasksize) == 0
+        @test !all(iszero, mask)
+        @test jl_setaffinity(0, mask, cpumasksize) == 0
     end
 end