diff --git a/src/sandbox.jl b/src/sandbox.jl
index 6efaf9ac..a95a073b 100644
--- a/src/sandbox.jl
+++ b/src/sandbox.jl
@@ -355,11 +355,18 @@ function setup_julia_sandbox(config::Configuration, args=``;
 
     # restrict resource usage
     if !isempty(config.cpus)
-        env["JULIA_CPU_THREADS"] = string(length(config.cpus)) # JuliaLang/julia#35787
-        env["OPENBLAS_NUM_THREADS"] = string(length(config.cpus)) # defaults to Sys.CPU_THREADS
-        env["JULIA_NUM_PRECOMPILE_TASKS"] = string(length(config.cpus)) # defaults to Sys.CPU_THREADS
+        # we might not always have CPU limiting capabilities (e.g. JuliaLang/julia#35787),
+        # so also instruct Julia to limit the number of threads it thinks are available
+        env["JULIA_CPU_THREADS"] = string(length(config.cpus))
+
+        # these should default to Sys.CPU_THREADS, but it can't hurt to be explicit
+        env["OPENBLAS_NUM_THREADS"] = string(length(config.cpus))
+        env["JULIA_NUM_PRECOMPILE_TASKS"] = string(length(config.cpus))
     end
 
+    # configure threads
+    env["JULIA_NUM_THREADS"] = string(config.threads)
+
     setup_generic_sandbox(config, `$cmd $(Cmd(config.julia_flags)) $args`;
                           env, mounts, kwargs...)
 end
diff --git a/src/types.jl b/src/types.jl
index 31e30551..82bcbbe5 100644
--- a/src/types.jl
+++ b/src/types.jl
@@ -69,8 +69,9 @@ Base.@kwdef struct Configuration
     ## a list of environment variables to set in the sandbox
     env::Setting{Vector{String}} = Default(String[])
     ## a list of CPUs to restrict the Julia process to (or empty if unconstrained).
-    ## if set, JULIA_CPU_THREADS will also be set to a number equaling the number of CPUs.
     cpus::Setting{Vector{Int}} = Default(Int[])
+    ## how many threads the Julia process should use
+    threads::Setting{Int} = Default(1)
     ## whether to spawn a virtual X server and expose that to the sandbox
     xvfb::Setting{Bool} = Default(true)
     ## whether to run under record-replay (rr). traces will be uploaded to AWS S3, so you
@@ -118,7 +119,7 @@ function Base.show(io::IO, cfg::Configuration)
     println(io)
 
     println(io, "  # Execution properties")
-    show_setting.(["env", "cpus", "xvfb", "rr", "precompile", "compiled", "process_limit"])
+    show_setting.(["env", "cpus", "threads", "xvfb", "rr", "precompile", "compiled", "process_limit"])
     show_setting.(["log_limit", "memory_limit"], Base.format_bytes)
     show_setting.(["time_limit", "compile_time_limit"], durationstring)
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 42a1bd23..1a1f86d2 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -170,15 +170,33 @@ end
         @test results[1, :status] == :kill && results[1, :reason] == :log_limit
     end
 
-    if "cpuset" in PkgEval.get_cgroup_controllers() && Sys.CPU_THREADS > 1
+    if "cpuset" in PkgEval.get_cgroup_controllers()
     @testset "cpu" begin
         let config = Configuration(config; cpus=[0])
-            cpu_threads = parse(Int, chomp(sprint(stdout->PkgEval.evaluate_script(config, "println(Sys.CPU_THREADS)"; stdout))))
+            cpu_threads = parse(Int, chomp(sprint(stdout->PkgEval.sandboxed_cmd(config, `/bin/sh -c "nproc"`; stdout))))
             @test cpu_threads == 1
         end
     end
     end
 
+    # not really a cgroup resource constraint, but it fits here nicely
+    @testset "threads" begin
+        let config = Configuration(config; cpus=[0])
+            cpu_threads = parse(Int, chomp(sprint(stdout->PkgEval.evaluate_script(config, "println(Sys.CPU_THREADS)"; stdout))))
+            @test cpu_threads == 1
+
+            julia_threads = parse(Int, chomp(sprint(stdout->PkgEval.evaluate_script(config, "println(Threads.nthreads())"; stdout))))
+            @test julia_threads == 1
+        end
+        let config = Configuration(config; cpus=[0], threads=8)
+            cpu_threads = parse(Int, chomp(sprint(stdout->PkgEval.evaluate_script(config, "println(Sys.CPU_THREADS)"; stdout))))
+            @test cpu_threads == 1
+
+            julia_threads = parse(Int, chomp(sprint(stdout->PkgEval.evaluate_script(config, "println(Threads.nthreads())"; stdout))))
+            @test julia_threads == 8
+        end
+    end
+
     if "pids" in PkgEval.get_cgroup_controllers()
     @testset "process" begin
         let config = Configuration(config; process_limit=1)