diff --git a/Android.bp b/Android.bp
index 0fd4ffe..a5a4d54 100644
--- a/Android.bp
+++ b/Android.bp
@@ -51,7 +51,6 @@
         "-DBORINGSSL_SHARED_LIBRARY",
         "-DBORINGSSL_ANDROID_SYSTEM",
         "-DOPENSSL_SMALL",
-        "-D_XOPEN_SOURCE=700",
         "-Werror",
         "-Wno-unused-parameter",
     ],
@@ -66,6 +65,12 @@
     // Build BoringSSL and its tests against the same STL.
     sdk_version: "9",
     target: {
+        linux: {
+            cflags: ["-D_XOPEN_SOURCE=700"],
+        },
+        windows: {
+            cflags: ["-D_XOPEN_SOURCE=700"],
+        },
         android: {
             stl: "libc++_static",
         },