diff --git a/lib/chibi/process.sld b/lib/chibi/process.sld
index 516aa3c0..2744a26e 100644
--- a/lib/chibi/process.sld
+++ b/lib/chibi/process.sld
@@ -1,6 +1,6 @@
 
 (define-library (chibi process)
-  (export exit sleep alarm fork kill execute waitpid system
+  (export exit sleep alarm %fork fork kill execute waitpid system
           process-command-line  process-running?
           set-signal-action! make-signal-set
           signal-set? signal-set-contains?
diff --git a/lib/chibi/process.stub b/lib/chibi/process.stub
index 71d5e7db..8714267d 100644
--- a/lib/chibi/process.stub
+++ b/lib/chibi/process.stub
@@ -90,10 +90,13 @@
 (define-c unsigned-int sleep (unsigned-int))
 
 ;;> Fork the current process.  Returns \rawcode{0} for the newly
-;;> created process, and the process id of the new process for
-;;> the parent.
+;;> created process, and the process id of the new process for the
+;;> parent.  If multiple threads are active, they are forked as well.
+;;> Use \scheme{fork} to also kill all other threads.
 
-(define-c pid_t fork ())
+(define-c pid_t (%fork fork) ())
+
+(define-c pid_t (fork sexp_fork_and_kill_threads) ((value ctx sexp)))
 
 (define-c-const int (wait/no-hang "WNOHANG"))
 
diff --git a/lib/chibi/signal.c b/lib/chibi/signal.c
index c82cf16b..10591a4f 100644
--- a/lib/chibi/signal.c
+++ b/lib/chibi/signal.c
@@ -117,6 +117,18 @@ static sexp sexp_pid_cmdline (sexp ctx, int pid) {
 
 #endif
 
+static pid_t sexp_fork_and_kill_threads (sexp ctx) {
+  pid_t res = fork();
+#if SEXP_USE_GREEN_THREADS
+  if (res == 0) {               /* child */
+    sexp_global(ctx, SEXP_G_THREADS_FRONT) = SEXP_NULL;
+    sexp_global(ctx, SEXP_G_THREADS_BACK) = SEXP_NULL;
+    sexp_global(ctx, SEXP_G_THREADS_PAUSED) = SEXP_NULL;
+  }
+#endif
+  return res;
+}
+
 static void sexp_init_signals (sexp ctx, sexp env) {
   call_sigaction.sa_sigaction  = sexp_call_sigaction;
 #if SEXP_USE_GREEN_THREADS