diff --git a/libc/tools/gensyscalls.py b/libc/tools/gensyscalls.py
index 2fa4e0f..01c580f 100755
--- a/libc/tools/gensyscalls.py
+++ b/libc/tools/gensyscalls.py
@@ -26,7 +26,8 @@
 # Make sure the directory is deleted when the script exits.
 atexit.register(shutil.rmtree, bionic_temp)
 
-bionic_libc_root = os.path.join(os.environ["ANDROID_BUILD_TOP"], "bionic/libc")
+bionic_libc_root = os.path.join(os.path.dirname(os.path.abspath(__file__)),
+                                "..")
 
 warning = "Generated by gensyscalls.py. Do not edit."