diff --git a/base/options.jl b/base/options.jl
index e0e1750d14cae..a94936391fa8d 100644
--- a/base/options.jl
+++ b/base/options.jl
@@ -11,7 +11,6 @@ struct JLOptions
     cpu_target::Ptr{UInt8}
     nthreadpools::Int16
     nthreads::Int16
-    ngcthreads::Int16
     nmarkthreads::Int16
     nsweepthreads::Int8
     nthreads_per_pool::Ptr{Int16}
diff --git a/base/threadingconstructs.jl b/base/threadingconstructs.jl
index 0854048e6b96c..b8a522be96d97 100644
--- a/base/threadingconstructs.jl
+++ b/base/threadingconstructs.jl
@@ -134,6 +134,7 @@ end
     Threads.ngcthreads() -> Int
 
 Returns the number of GC threads currently configured.
+This includes both mark threads and concurrent sweep threads.
 """
 ngcthreads() = Int(unsafe_load(cglobal(:jl_n_gcthreads, Cint))) + 1
 
diff --git a/src/jloptions.c b/src/jloptions.c
index f82e46ca9a4a5..129ba9df2510e 100644
--- a/src/jloptions.c
+++ b/src/jloptions.c
@@ -40,7 +40,6 @@ JL_DLLEXPORT void jl_init_options(void)
                         NULL, // cpu_target ("native", "core2", etc...)
                         0,    // nthreadpools
                         0,    // nthreads
-                        0,    // ngcthreads
                         0,    // nmarkthreads
                         0,    // nsweepthreads
                         NULL, // nthreads_per_pool
diff --git a/src/jloptions.h b/src/jloptions.h
index 9f74d520e59ff..8649c405112d7 100644
--- a/src/jloptions.h
+++ b/src/jloptions.h
@@ -15,7 +15,6 @@ typedef struct {
     const char *cpu_target;
     int8_t nthreadpools;
     int16_t nthreads;
-    int16_t ngcthreads;
     int16_t nmarkthreads;
     int8_t nsweepthreads;
     const int16_t *nthreads_per_pool;
diff --git a/stdlib/Distributed/src/cluster.jl b/stdlib/Distributed/src/cluster.jl
index 6dc6bd086df16..0c865b8d1b3a8 100644
--- a/stdlib/Distributed/src/cluster.jl
+++ b/stdlib/Distributed/src/cluster.jl
@@ -1331,6 +1331,14 @@ function get_threads_spec(opts)
     end
 end
 
+function get_gcthreads_spec(opts)
+    if opts.markthreads > 0 || opts.sweepthreads > 0
+        `--gcthreads=$(opts.markthreads),$(opts.sweepthreads)`
+    else
+        ``
+    end
+end
+
 # Starts workers specified by (-n|--procs) and --machine-file command line options
 function process_opts(opts)
     # startup worker.
@@ -1346,7 +1354,8 @@ function process_opts(opts)
 
     # Propagate --threads to workers
     threads = get_threads_spec(opts)
-    gcthreads = opts.ngcthreads > 0 ? `--gcthreads=$(opts.ngcthreads)` : ``
+    # Propagate --gcthreads to workers
+    gcthreads = get_gcthreads_spec(opts)
 
     exeflags = `$threads $gcthreads`
 
diff --git a/test/cmdlineargs.jl b/test/cmdlineargs.jl
index 21567468ffe9e..917031b57fe5f 100644
--- a/test/cmdlineargs.jl
+++ b/test/cmdlineargs.jl
@@ -362,12 +362,19 @@ let exename = `$(Base.julia_cmd()) --startup-file=no --color=no`
         withenv("JULIA_NUM_GC_THREADS" => nt) do
             @test read(`$exename --gcthreads=2 -e $code`, String) == "2"
         end
+        withenv("JULIA_NUM_GC_THREADS" => nt) do
+            @test read(`$exename --gcthreads=2,1 -e $code`, String) == "3"
+        end
     end
 
     withenv("JULIA_NUM_GC_THREADS" => 2) do
         @test read(`$exename -e $code`, String) == "2"
     end
 
+    withenv("JULIA_NUM_GC_THREADS" => "2,1") do
+        @test read(`$exename -e $code`, String) == "3"
+    end
+
     # --machine-file
     # this does not check that machine file works,
     # only that the filename gets correctly passed to the option struct
diff --git a/test/gc.jl b/test/gc.jl
index ecf71fe51f6ad..861483bf246a3 100644
--- a/test/gc.jl
+++ b/test/gc.jl
@@ -5,9 +5,10 @@ using Test
 function run_gctest(file)
     let cmd = `$(Base.julia_cmd()) --depwarn=error --rr-detach --startup-file=no $file`
         @testset for test_nthreads in (1, 2, 4)
+            @testset for concurrent_sweep in (0, 1)
             new_env = copy(ENV)
             new_env["JULIA_NUM_THREADS"] = string(test_nthreads)
-            new_env["JULIA_NUM_GC_THREADS"] = string(test_nthreads)
+            new_env["JULIA_NUM_GC_THREADS"] = "$(test_nthreads),$(concurrent_sweep)"
             @test success(run(pipeline(setenv(cmd, new_env), stdout = stdout, stderr = stderr)))
         end
     end