diff --git a/libc/include/bits/posix_limits.h b/libc/include/bits/posix_limits.h
index db09bd795..cfc46f5c6 100644
--- a/libc/include/bits/posix_limits.h
+++ b/libc/include/bits/posix_limits.h
@@ -99,7 +99,7 @@
 #define _POSIX_THREAD_PRIORITY_SCHEDULING 200809L
 #define _POSIX_THREAD_PRIO_INHERIT -1  /* not implemented */
 #define _POSIX_THREAD_PRIO_PROTECT -1  /* not implemented */
-#define _POSIX_THREAD_PROCESS_SHARED  -1  /* not implemented */
+#define _POSIX_THREAD_PROCESS_SHARED  200809L  /* PTHREAD_PROCESS_SHARED supported. */
 #define _POSIX_THREAD_ROBUST_PRIO_INHERIT -1  /* not implemented */
 #define _POSIX_THREAD_ROBUST_PRIO_PROTECT -1  /* not implemented */
 #define _POSIX_THREAD_SAFE_FUNCTIONS 200809L
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index 9eae06ec0..109b92cc8 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -742,6 +742,7 @@ TEST(UNISTD_TEST, _POSIX_macros_smoke) {
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_PRIORITY_SCHEDULING);
   EXPECT_EQ(-1, _POSIX_THREAD_PRIO_INHERIT);
   EXPECT_EQ(-1, _POSIX_THREAD_PRIO_PROTECT);
+  EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_PROCESS_SHARED);
   EXPECT_EQ(-1, _POSIX_THREAD_ROBUST_PRIO_PROTECT);
   EXPECT_EQ(_POSIX_VERSION, _POSIX_THREAD_SAFE_FUNCTIONS);
   EXPECT_EQ(-1, _POSIX_THREAD_SPORADIC_SERVER);
@@ -781,7 +782,6 @@ TEST(UNISTD_TEST, _POSIX_macros_smoke) {
   EXPECT_EQ(-1, _POSIX_PRIORITIZED_IO);
   EXPECT_EQ(-1, _POSIX_SHARED_MEMORY_OBJECTS);
   EXPECT_EQ(-1, _POSIX_SPAWN);
-  EXPECT_EQ(-1, _POSIX_THREAD_PROCESS_SHARED);
   EXPECT_EQ(-1, _POSIX_THREAD_ROBUST_PRIO_INHERIT);
 
   EXPECT_EQ(-1, _POSIX2_VERSION);
@@ -908,6 +908,7 @@ TEST(UNISTD_TEST, sysconf) {
   VERIFY_SYSCONF_UNSUPPORTED(_SC_SPORADIC_SERVER);
   VERIFY_SYSCONF_POSITIVE(_SC_SYMLOOP_MAX);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_THREAD_CPUTIME);
+  VERIFY_SYSCONF_POSIX_VERSION(_SC_THREAD_PROCESS_SHARED);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_THREAD_SPORADIC_SERVER);
   VERIFY_SYSCONF_POSIX_VERSION(_SC_TIMEOUTS);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_TRACE);
@@ -944,7 +945,6 @@ TEST(UNISTD_TEST, sysconf) {
   VERIFY_SYSCONF_UNSUPPORTED(_SC_PRIORITIZED_IO);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_SHARED_MEMORY_OBJECTS);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_SPAWN);
-  VERIFY_SYSCONF_UNSUPPORTED(_SC_THREAD_PROCESS_SHARED);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_THREAD_ROBUST_PRIO_INHERIT);
   VERIFY_SYSCONF_UNSUPPORTED(_SC_THREAD_ROBUST_PRIO_PROTECT);