--- a/lang/american.txt	Fri Dec 08 12:31:34 2006 +0000
+++ b/lang/american.txt	Fri Dec 08 17:40:42 2006 +0000
@@ -2906,6 +2906,7 @@
 STR_NEWGRF_ADD_FILE_TIP                                         :{BLACK}Add the selected NewGRF file to your configuration
 STR_NEWGRF_RESCAN_FILES                                         :{BLACK}Rescan files
 STR_NEWGRF_RESCAN_FILES_TIP                                     :{BLACK}Update the list of available NewGRF files
+STR_NEWGRF_DUPLICATE_GRFID                                      :{WHITE}Cannot add file: duplicate GRF ID
 
 STR_NEWGRF_NOT_FOUND                                            :{RED}Matching file not found
 STR_NEWGRF_DISABLED                                             :{RED}Disabled