diff --git a/acconfig.h b/acconfig.h
index 4ab3aa2..685b41c 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -51,3 +51,8 @@
 #undef size_t
 #undef ssize_t
 #undef socklen_t
+
+/*
+ * A string containing the name of the system tinyproxy was built towards.
+ */
+#undef TARGET_SYSTEM