--- a/libgrit/grit_prep.cpp
+++ b/libgrit/grit_prep.cpp
@@ -562,7 +562,7 @@
 	mf= gr->msFormat;
 
 	tileN= tmap_get_tilecount(map);
-	if(tileN >= (1<<mf.idLen))
+	if(tileN > (1<<mf.idLen))
 	{
 		lprintf(LOG_ERROR, "Number of tiles (%d) exceeds field limit (%d).\n", 
 			tileN, 1<<mf.idLen);