diff --git a/lib/careadlinkat.h b/lib/careadlinkat.h
index 84ede3e..8e8f42e 100644
--- a/lib/careadlinkat.h
+++ b/lib/careadlinkat.h
@@ -23,6 +23,10 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#ifndef AT_FDCWD
+#define AT_FDCWD -2
+#endif
+
 struct allocator;
 
 /* Assuming the current directory is FD, get the symbolic link value