diff -r d7ee0a65ead9 -r 999eb7531205 src/ai/api/ai_cargo.hpp
--- a/src/ai/api/ai_cargo.hpp	Tue Mar 20 00:12:35 2007 +0000
+++ b/src/ai/api/ai_cargo.hpp	Tue Mar 20 00:14:29 2007 +0000
@@ -17,7 +17,7 @@
 	 * @param cargo_type the cargo to check.
 	 * @return true if and only if the cargo type is valid.
 	 */
-	bool IsValidCargo(CargoID cargo_type);
+	static bool IsValidCargo(CargoID cargo_type);
 
 	/**
 	 * Gets the string representation of the cargo label.