diff --git a/libcork/posix/subprocess.c b/libcork/posix/subprocess.c
index 75f1c4e5..a3014662 100644
--- a/libcork/posix/subprocess.c
+++ b/libcork/posix/subprocess.c
@@ -511,7 +511,7 @@ cork_subprocess_is_finished(struct cork_subprocess *self)
 #if defined(__APPLE__) || defined(__MINGW32__) || defined(__CYGWIN__)
 #include <pthread.h>
 #define THREAD_YIELD   pthread_yield_np
-#elif defined(__linux__) || defined(BSD)
+#elif defined(__linux__) || defined(BSD) || defined(__sun)
 #include <sched.h>
 #define THREAD_YIELD   sched_yield
 #else