--- a/pylib/gyp/xcode_emulation.py
+++ b/pylib/gyp/xcode_emulation.py
@@ -1470,7 +1470,8 @@
     sdk_root = xcode_settings._SdkRoot(configuration)
     if not sdk_root:
       sdk_root = xcode_settings._XcodeSdkPath('')
-    env['SDKROOT'] = sdk_root
+    if sdk_root:
+      env['SDKROOT'] = sdk_root
 
   if not additional_settings:
     additional_settings = {}