diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index a81f112..28f19a1 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -775,6 +775,12 @@
   EXPECT_GT(_XOPEN_IOV_MAX, 0);
   EXPECT_GT(_XOPEN_UNIX, 0);
 
+  // In O, the headers still have -1 (even though all the functionality has
+  // been there for a long time). This was fixed in O-DR, but there isn't a
+  // separate CTS for O-DR, so we'll accept both.
+  EXPECT_TRUE(_POSIX_THREAD_PROCESS_SHARED == -1 ||
+              _POSIX_THREAD_PROCESS_SHARED == _POSIX_VERSION);
+
 #if defined(__BIONIC__)
   // These tests only pass on bionic, as bionic and glibc has different support on these macros.
   // Macros like _POSIX_ASYNCHRONOUS_IO are not supported on bionic yet.