diff --git a/base/sysinfo.jl b/base/sysinfo.jl
index 484ac4d01d104..3cb95396502a9 100644
--- a/base/sysinfo.jl
+++ b/base/sysinfo.jl
@@ -147,7 +147,7 @@ function __init__()
     end
     global CPU_THREADS = if env_threads !== nothing
         env_threads = tryparse(Int, env_threads)
-        if !(env_threads isa Int && env_threads > 0)
+        if env_threads === nothing || env_threads <= 0
             env_threads = Int(ccall(:jl_cpu_threads, Int32, ()))
             Core.print(Core.stderr, "WARNING: couldn't parse `JULIA_CPU_THREADS` environment variable. Defaulting Sys.CPU_THREADS to $env_threads.\n")
         end