Index: lib/Basic/Targets/OSTargets.h
===================================================================
--- lib/Basic/Targets/OSTargets.h
+++ lib/Basic/Targets/OSTargets.h
@@ -362,8 +362,10 @@
     Builder.defineMacro("__NetBSD__");
     Builder.defineMacro("__unix__");
     Builder.defineMacro("__ELF__");
-    if (Opts.POSIXThreads)
+    if (Opts.POSIXThreads) {
       Builder.defineMacro("_REENTRANT");
+      Builder.defineMacro("_PTHREADS");
+    }
   }
 
 public:
Index: test/Driver/netbsd.c
===================================================================
--- test/Driver/netbsd.c
+++ test/Driver/netbsd.c
@@ -431,5 +431,6 @@
 // S-POWERPC64: "{{.*}}/usr/lib{{/|\\\\}}crtend.o" "{{.*}}/usr/lib{{/|\\\\}}crtn.o"
 
 // PTHREAD-NOT: _POSIX_THREADS
+// PTHREAD:     _PTHREADS
 // PTHREAD:     _REENTRANT
 // PTHREAD-NOT: _POSIX_THREADS