diff --git a/dl/BUILD.gn b/dl/BUILD.gn
index 04b40d3..7dc755c 100644
--- a/dl/BUILD.gn
+++ b/dl/BUILD.gn
@@ -102,7 +102,9 @@
   }
 
   if (current_cpu == "x86" || current_cpu == "x64") {
-    cflags += [ "-msse2" ]
+    if (is_posix) {
+      cflags += [ "-msse2" ]
+    }
 
     sources += [
       # Real 32-bit floating-point FFT.
diff --git a/dl/dl.gyp b/dl/dl.gyp
index 37e94a7..27d7508 100644
--- a/dl/dl.gyp
+++ b/dl/dl.gyp
@@ -120,8 +120,13 @@
           ],
         }],
         ['target_arch=="ia32" or target_arch=="x64"', {
-          'cflags': [
-            '-msse2',
+          'conditions': [
+            ['os_posix==1', {
+              'cflags': [ '-msse2', ],
+              'xcode_settings': {
+                'OTHER_CFLAGS': [ '-msse2', ],
+              },
+            }],
           ],
           'sources': [
             # Real 32-bit floating-point FFT.