diff -Naurp a/NTS/config.m4 b/NTS/config.m4
--- a/NTS/config.m4	2019-07-05 09:18:10.983115724 +0000
+++ b/NTS/config.m4	2019-07-18 16:03:38.791414805 +0000
@@ -681,7 +681,7 @@ if test "$PHP_GRPC" != "no"; then
     , $ext_shared, , -fvisibility=hidden \
     -DOPENSSL_NO_ASM -D_GNU_SOURCE -DWIN32_LEAN_AND_MEAN \
     -D_HAS_EXCEPTIONS=0 -DNOMINMAX -DGRPC_ARES=0 \
-    -DGRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK=1)
+    )
 
   PHP_ADD_BUILD_DIR($ext_builddir/src/php/ext/grpc)