diff --git a/embed.fnc b/embed.fnc
index 5ddab55acec8..d0a478e98aa4 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -678,6 +678,7 @@ Apx	|void	|apply_attrs_string					\
 Adp	|OP *	|apply_builtin_cv_attributes				\
 				|NN CV *cv				\
 				|NULLOK OP *attrlist
+CTp	|void	|atfork_child
 CTp	|void	|atfork_lock
 CTp	|void	|atfork_unlock
 Cop	|SV **	|av_arylen_p	|NN AV *av
diff --git a/embed.h b/embed.h
index 9c5c2a8acf04..13aaf21b90fd 100644
--- a/embed.h
+++ b/embed.h
@@ -130,6 +130,7 @@
 # define amagic_deref_call(a,b)                 Perl_amagic_deref_call(aTHX_ a,b)
 # define apply_attrs_string(a,b,c,d)            Perl_apply_attrs_string(aTHX_ a,b,c,d)
 # define apply_builtin_cv_attributes(a,b)       Perl_apply_builtin_cv_attributes(aTHX_ a,b)
+# define atfork_child                           Perl_atfork_child
 # define atfork_lock                            Perl_atfork_lock
 # define atfork_unlock                          Perl_atfork_unlock
 # define av_clear(a)                            Perl_av_clear(aTHX_ a)
diff --git a/ext/ExtUtils-Miniperl/lib/ExtUtils/Miniperl.pm b/ext/ExtUtils-Miniperl/lib/ExtUtils/Miniperl.pm
index d7d4b714118c..c6117385bc05 100644
--- a/ext/ExtUtils-Miniperl/lib/ExtUtils/Miniperl.pm
+++ b/ext/ExtUtils-Miniperl/lib/ExtUtils/Miniperl.pm
@@ -5,7 +5,7 @@ use Exporter 'import';
 use ExtUtils::Embed 1.31, qw(xsi_header xsi_protos xsi_body);
 
 our @EXPORT = qw(writemain);
-our $VERSION = '1.14';
+our $VERSION = '1.15';
 
 # blead will run this with miniperl, hence we can't use autodie or File::Temp
 my $temp;
@@ -122,7 +122,7 @@ main(int argc, char **argv, char **env)
      * --GSAR 2001-07-20 */
     PTHREAD_ATFORK(Perl_atfork_lock,
                    Perl_atfork_unlock,
-                   Perl_atfork_unlock);
+                   Perl_atfork_child);
 #endif
 
     PERL_SYS_FPU_INIT;
diff --git a/ext/XS-APItest/APItest.pm b/ext/XS-APItest/APItest.pm
index 9543147488f8..2ff6b1ecb7b3 100644
--- a/ext/XS-APItest/APItest.pm
+++ b/ext/XS-APItest/APItest.pm
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 use Carp;
 
-our $VERSION = '1.43';
+our $VERSION = '1.44';
 
 require XSLoader;
 
diff --git a/ext/XS-APItest/APItest.xs b/ext/XS-APItest/APItest.xs
index f2d2774a655a..90caa7c2c410 100644
--- a/ext/XS-APItest/APItest.xs
+++ b/ext/XS-APItest/APItest.xs
@@ -1601,6 +1601,17 @@ destruct_test(pTHX_ void *p) {
     warn("In destruct_test: %" SVf "\n", (SV*)p);
 }
 
+#if defined(USE_ITHREADS) && !defined(WIN32)
+
+static void *
+signal_thread_start(void *arg) {
+  PERL_UNUSED_ARG(arg);
+  raise(SIGUSR1);
+  return NULL;
+}
+
+#endif
+
 #ifdef PERL_USE_HWM
 #  define hwm_checks_enabled() true
 #else
@@ -4367,6 +4378,21 @@ CODE:
 OUTPUT:
     RETVAL
 
+pthread_t
+make_signal_thread()
+CODE:
+    if (pthread_create(&RETVAL, NULL, signal_thread_start, NULL) != 0)
+        XSRETURN_EMPTY;
+OUTPUT:
+    RETVAL
+
+int
+join_signal_thread(pthread_t tid)
+CODE:
+    RETVAL = pthread_join(tid, NULL);
+OUTPUT:
+    RETVAL
+
 #  endif /* ifndef WIN32 */
 
 #endif /* USE_ITHREADS */
diff --git a/ext/XS-APItest/t/thread.t b/ext/XS-APItest/t/thread.t
index fe5ac953ba34..4c4c88785f09 100644
--- a/ext/XS-APItest/t/thread.t
+++ b/ext/XS-APItest/t/thread.t
@@ -1,7 +1,8 @@
 #!perl
 use warnings;
 use strict;
-use Test2::Tools::Basic;
+use Test2::IPC;
+use Test2::V0;
 use Config;
 
 BEGIN {
@@ -9,9 +10,63 @@ BEGIN {
       if !$Config{usethreads} || $^O eq "MSWin32";
 }
 
-use XS::APItest qw(thread_id_matches);
+use XS::APItest qw(thread_id_matches make_signal_thread join_signal_thread);
 
 ok(thread_id_matches(),
    "check main thread id saved and is current thread");
 
+# This test isn't too useful on Linux, it passes without the fix.
+#
+# thread ids are unique only within a process, so it's valid for Linux
+# pthread_self() to return the same id for the main thread after a
+# fork.
+#
+# This may be different on other POSIX-likes.
+SKIP:
+{
+    $Config{d_fork}
+      or skip "Need fork", 1;
+    my $pid = fork;
+    defined $pid
+      or skip "Fork failed", 1;
+    if ($pid == 0) {
+        ok(thread_id_matches(), "check main thread id is updated by fork");
+        exit;
+    }
+    else {
+        waitpid($pid, 0);
+    }
+}
+
+{
+    $Config{d_fork}
+      or skip "Need fork", 1;
+    my $pid = fork;
+    defined $pid
+      or skip "Fork failed", 1;
+    if ($pid == 0) {
+        # ensure the main thread saved is valid after fork
+        my $saw_signal;
+        local $SIG{USR1} = sub { ++$saw_signal };
+        my $pid = make_signal_thread();
+        join_signal_thread($pid);
+        ok($saw_signal, "saw signal sent to non-perl thread in child");
+        exit 0;
+    }
+    else {
+        is(waitpid($pid, 0), $pid, "wait child");
+        # catches the child segfaulting for example
+        is($?, 0, "child success");
+    }
+}
+
+{
+    my $saw_signal;
+    local $SIG{USR1} = sub { ++$saw_signal };
+    my $pid = make_signal_thread();
+    join_signal_thread($pid);
+    ok($saw_signal, "saw signal sent to non-perl thread");
+}
+
+
 done_testing();
diff --git a/ext/XS-APItest/typemap b/ext/XS-APItest/typemap
index f4c401eba2c3..08840e090901 100644
--- a/ext/XS-APItest/typemap
+++ b/ext/XS-APItest/typemap
@@ -3,12 +3,27 @@ XS::APItest::PtrTable		T_PTROBJ
 const WCHAR *			WPV
 U8 *		                T_PV
 
+pthread_t			T_THREADID
+
 INPUT
 
 WPV
         $var = ($type)SvPV_nolen($arg);
 
+T_THREADID
+        {
+          STRLEN len;
+          const char *pv = SvPVbyte($arg, len);
+          if (len != sizeof(pthread_t))
+            croak(\"Bad thread id for $arg\");
+          Copy(pv, &$var, 1, pthread_t);
+        }
+
 OUTPUT
 
 WPV
         sv_setpvn($arg, (const char *)($var), sizeof(WCHAR) * (1+wcslen($var)));
+
+T_THREADID
+        sv_setpvn($arg, (const char *)&($var), sizeof($var));
+        SvUTF8_off($arg);
diff --git a/miniperlmain.c b/miniperlmain.c
index 38951e002753..64ee56830f07 100644
--- a/miniperlmain.c
+++ b/miniperlmain.c
@@ -96,7 +96,7 @@ main(int argc, char **argv, char **env)
      * --GSAR 2001-07-20 */
     PTHREAD_ATFORK(Perl_atfork_lock,
                    Perl_atfork_unlock,
-                   Perl_atfork_unlock);
+                   Perl_atfork_child);
 #endif
 
     PERL_SYS_FPU_INIT;
diff --git a/proto.h b/proto.h
index a7e81e069149..38313d5e991a 100644
--- a/proto.h
+++ b/proto.h
@@ -210,6 +210,10 @@ Perl_apply_builtin_cv_attributes(pTHX_ CV *cv, OP *attrlist);
 #define PERL_ARGS_ASSERT_APPLY_BUILTIN_CV_ATTRIBUTES \
         assert(cv); assert(SvTYPE(cv) == SVt_PVCV || SvTYPE(cv) == SVt_PVFM)
 
+PERL_CALLCONV void
+Perl_atfork_child(void);
+#define PERL_ARGS_ASSERT_ATFORK_CHILD
+
 PERL_CALLCONV void
 Perl_atfork_lock(void);
 #define PERL_ARGS_ASSERT_ATFORK_LOCK
diff --git a/util.c b/util.c
index 7cf7a7629536..f7ce5884763b 100644
--- a/util.c
+++ b/util.c
@@ -2872,6 +2872,18 @@ Perl_atfork_unlock(void)
 #endif
 }
 
+void
+Perl_atfork_child(void) {
+#ifdef USE_ITHREADS
+    /* so we can resend signals received in a non-perl thread to the
+       new main thread
+    */
+    PTHREAD_INIT_SELF(PL_main_thread);
+#endif
+
+    Perl_atfork_unlock();
+}
+
 /*
 =for apidoc_section $concurrency
 =for apidoc my_fork