ha_innodb.cc:

  InnoDB maps HA_READ_PREFIX_LAST_OR_PREV to PAGE_CUR_LE, but note that only complete-field prefixes of the kay value can be used as the search key

sql/ha_innodb.cc

@@ -2293,6 +2293,7 @@ convert_search_mode_to_innobase(
 		case HA_READ_BEFORE_KEY:	return(PAGE_CUR_L);
 		case HA_READ_PREFIX:		return(PAGE_CUR_GE);
 	        case HA_READ_PREFIX_LAST:       return(PAGE_CUR_LE);
+	        case HA_READ_PREFIX_LAST_OR_PREV:return(PAGE_CUR_LE);
 		  /* In MySQL HA_READ_PREFIX and HA_READ_PREFIX_LAST always
 		  use a complete-field-prefix of a kay value as the search
 		  tuple. I.e., it is not allowed that the last field would