diff --git a/setup.py b/setup.py
index 20d7f35..b168ed4 100644
--- a/setup.py
+++ b/setup.py
@@ -146,7 +146,7 @@
         return MACOS_SDK_ROOT
 
     cflags = sysconfig.get_config_var('CFLAGS')
-    m = re.search(r'-isysroot\s+(\S+)', cflags)
+    m = re.search(r'-isysroot\s*(\S+)', cflags)
     if m is not None:
         MACOS_SDK_ROOT = m.group(1)
     else: