diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 8203ade..ccb46a6 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -660,8 +660,9 @@ def _use_posix_spawn():
         # os.posix_spawn() is not available
         return False
 
-    if sys.platform == 'darwin':
-        # posix_spawn() is a syscall on macOS and properly reports errors
+    if sys.platform in ('darwin', 'sunos5'):
+        # posix_spawn() is a syscall on both macOS and Solaris,
+        # and properly reports errors
         return True
 
     # Check libc name and runtime libc version