--- a/config/system-headers.mozbuild
+++ b/config/system-headers.mozbuild
@@ -864,7 +864,6 @@
     "sys/shm.h",
     "sys/siginfo.h",
     "sys/signal.h",
-    "sys/single_threaded.h",
     "sys/socket.h",
     "sys/sockio.h",
     "sys/sparc/frame.h",