diff -r b2cc6f31363c -r 5f26f4bc574b src/ai/api/ai_sign.hpp
--- a/src/ai/api/ai_sign.hpp	Sun Mar 25 15:22:56 2007 +0000
+++ b/src/ai/api/ai_sign.hpp	Sun Mar 25 16:10:40 2007 +0000
@@ -13,6 +13,11 @@
 class AISign : public AIObject {
 public:
 	/**
+	 * The name of the class, needed by several sub-processes.
+	 */
+	static const char *GetClassName() { return "AISign"; }
+
+	/**
 	 * Gets the maximum sign index; there are no valid signs with a higher index.
 	 * @return the maximum sign index.
 	 * @post return value is always non-negative.